Tough question Kenny and everyone has covered most of the points. I personally have windsurfed and kitesurfed for over 10 years as I cross back forth between the sports.
The big positives with kiting are:
Its cheaper to maintain and update equipment
The equipment is so much more compact and fits inside of most small cars
The wind range is greater for kitesurfing
The negatives are:
You need a large launch area
There are loads of d!ckheads now kiting as it becomes more accessible
When things go wrong they really go wrong. This is where safety and common sense must prevail but even still people continue to have serious accidents.
As for windsurfing you almost feel like you're at one with the board and sail and its a great feeling to rip across the chop but it will take you probably twice as many sessions to get to this stage compared with kiting. I also think kitesurfing in the surf is easier (providing your kite stays in the air) as you can accelerate and turn much faster to avoid the breakers.
Also from past experience sailing/surfing experience helps very little as you will soon find out with exception to wind knowledge.
Good luck, but I think either will be rewarding sports.
If you can make it up to Elanda point lake Cootharaba over the next week I'll be happy to help you out with getting started. Not much further along myself but there will be a group of us beginner/intermediates with learning gear and shallow flat water. Gentle winds forcast.
Started at 55 and only 3 years in :-). Loving windsurfing - reckon I'll hurt myself badly with kites.
Cheers Jeff
G'day KennyK,
I started windsurfing last year at 45 and having a great time. Time on the water is the most important asset you can have in this sport. So work out which sport will give you the most time on the water. Which is what everybody is after.
Coming from a surfing/ sailing background where you will have water skills and knowledge of how a sail works should make windsurfing a bit easier to pick up.
Its a full body workout and you will be sore after some sails but beer usually sorts that out.
So grab yourself a 140 odd litre Freeride board and a couple of sails and get out there. Try and spend a few dollars on good quality masts, base, extension and boom so that you have a good base to buy other gear around if you like.
Cheers PK
Some thoughts from Italy, where lack of consistent waves makes the choice different.
I do not kite but it's evident that one can learn kiting much much faster than windsurfing; and, if TOW needed to learn how to go out and come back can be just 2 x time for windsurfing, the most important difference is in TOW needed to enter the realm of "high performance" (jumps, fast runs, carves, ...), there I'd say it's 10 x for windsurfing.
The big, big "down" for kitesurfing is, as some already pointed out, ugly company. "Show" kiting is way easier than "show" windsurfing and this lead lots of "show" idiots into the sport. Usually they know nothing or so about how to behave on the water and put at huge risk both themselves (which would not be a problem, but just natural evolution) and others. This past Summer I saw a child of maybe 8 - 10 years with her face and neck badly bruised by the lines of one such idiot who couldn't avoid manouvering as close to the beach as his short fins let him. Must admit I also saw quite a few accidents between windsurfers, but never anything that wasn't solved with a brief chat, a hand shake and sometimes some money going into another wallet.
So better stay away from kiters if possible.
Another "down" with kitesurfing is, true, when things get tough with kites they get really tough; but it seems to me that advancements in materials drove the alarm level way up; making both for generally less dangerous situatons, and for less confidence with those when happen.
I have some friends that used to be avid windsurfers and are kiters now; of course they have lots of experience and do not belong to the "idiot" category; and some of them admit they had to pick up kiting because of physical problems with their spines, and still admit "windsurfing was a different thing". And, luckily, in my spot there seems to be a consistent trend with less kiters and more windsurfers.
Select to expand quoteKennyK said..Gestalt said..
depending on how big your sup is you can probably have a go at learning windsurfing on it.
best conditions for sup sailing in light winds are 5-10 knots cross to cross offshore. with sup you don't need footstraps so you can walk about the board like a surfboard. if the day is better for surfing then go surfing. if it's a good sup day put on a 5.8m sail
this video looks to be less 5 knots.
here is a photo I took at the Caloundra bar. - jp sup
shortboard wavesailing in 5-10 knots at Caloundra bar again. when the SW winds blow head down to happys
Thanks.
I called Deiter at Sunshine coast sail boards, he has a rig there that will suit my sup. It has a Gaastra Poison 5.4m sail, sound all right?
Ken.
yep that will do the job well. always try and get the right mast as well. the gaastras are mast specific. all sails need a particular bend curve to rig correctly.
I'd also take up jeff's gracious offer of a catchup at lake cootharaba.
I was also thinking you should keep an eye out for this windsurfing club. it's sunshine/fraser coast based.
www.windwanderers.org.au/
a lot of us on this forum are members and sail together. myself included.
Select to expand quotejirvin4505 said..
If you can make it up to Elanda point lake Cootharaba over the next week I'll be happy to help you out with getting started. Not much further along myself but there will be a group of us beginner/intermediates with learning gear and shallow flat water. Gentle winds forcast.
Started at 55 and only 3 years in :-). Loving windsurfing - reckon I'll hurt myself badly with kites.
Cheers Jeff
Thanks Jeff,
Appreciate your offer.
Are you up there on the weekend at all?
Ken.
the alpha was a very good sail.
I would not go any bigger than 6.4 for what you are chasing.
Snip.,,
Thanks Jeff,
Appreciate your offer.
Are you up there on the weekend at all?
Ken.
> sent a pm
Up there from tomorrow morning 
Cheers Jeff
Select to expand quoteKennyK said..
Hi Gestalt,
You are the only one that has said windsurfers can wave sail well in low wind conditions. I'd certainly like to know more please. Is there any video you can point me to? Or suggestions of what gear I may look at?
I have been for a long time thinking of getting a sail rig for my SUP and still will if I can find a cheap one that is suitable. Maybe this would be a good place to start?
Ken.
This is just to illustrate that if the wave has enough power, you just need enough wind to get into position for take-off. In this case, when the wind drops right off, he is having to use the jet ski to tow him most of the way back to the line-up. So you can use a small waveboard as long as you can get back to the take-off point. Once on the wave, you get sail power from the 'apparent' wind.
nice posts terminal. that last kauli vid is one of my favs.
there is also teahupoo in no wind.
www.dailymotion.com/video/x1yfxxg
and
cloud break no wind (4.30 onwards)
I windsurf and my two brother-in-laws kite surf. Most of the points have been made already but a couple more from me:
Windsurfing can handle crappy, gusty conditions way better and safer than kites. I sail all winter, they wait for the consistent summer seabreezes. A 5-30kt winter front is a recipe for disaster for a kite, for a windsurfer it can be fun bobbing around waiting for a big gust over flat water.
I think they need less gear. One of them has three kites and 3 boards to cover 10-30kts, flat water, freestyle and waves. Hard to do that with windsurfing gear and it takes up more space/harder to travel with.
Kiters do have an edge in low wind now (as little as 6 kts with the right gear) on flat water but I recall watching a big day at Margaret River where the kites were dropping out of the air yet talented young windsurfers would slowly float out and but once on a wave they were powered up and ripping and slashing. My chances of doing that are 2 fifths of... well let's just say I'm a realist.
Good luck with your choice, either way you're going to have fun.
float and ride does take a fairly high skill level.
I bought a supsail, bypass the skill part.
i had forgotten about this video. absolute corker. doesn't look to be any wind at all. kites would of dropped out of the sky long before this was shot.
Well I just bought myself a sail rig for my SUP.
It's the Gaastra Poison 5.4m rig.
It'll go on my 9'6" JP Surf pro.
Hopefully it'll work well for me?
Find out tomorrow I guess.
Thanks to every one for your help. 
And especially to Jeff who I will be helping me out with some pointers on Sunday.
Cheers,
Ken.
nice one ken hope you have fun! your sup is definitely big enough to learn on.
biggest tip i can give you is to keep your feet along the centreline of the board. once you get your weight over the rail you'll be in the water in no time.
you WILL need a lesson or 2 so don't be afraid to ask. i'll drop you a line in the next few weeks and see if you need any more help.
you might benefit from a few youtube vids on how to rig a sail and how to uphaul. those are the places to start.
Select to expand quoteGestalt said..
nice one ken hope you have fun! your sup is definitely big enough to learn on.
biggest tip i can give you is to keep your feet along the centreline of the board. once you get your weight over the rail you'll be in the water in no time.
you WILL need a lesson or 2 so don't be afraid to ask. i'll drop you a line in the next few weeks and see if you need any more help.
you might benefit from a few youtube vids on how to rig a sail and how to uphaul. those are the places to start.
Thanks alot Gestalt! 
Ken is on the water
Doing well. Hasn't fallen off yet. Already tacking and gybing
Cheers Jeff
Oops sorry about the orientation - will fix later
just to add to it, ive windsurfed since '83, started kiting in '99, and liked it until about 06-07..then it changed.
so started windsurfing again in '09. completely stoked on it..even for lightwind, id rather sail formula in lightwind, or sup sail if waves.. dont miss kiting at all, the lines, the pumping, the attitude. 
windsurfing just feels more connected.
although, the smaller gear in the trunk was nice, they take up just way too much room on the beach and the water.
it was fun for a while though.
maybe i'll go back to it again when im older.. who knows.
Went out today at Boreen point, (flat water 5-15 Knots).
Went well, mowed some grass, mostly tacking but got a gybe in as well. 
And a beach start to kick it off. Got some great advice and help from Jeff, off this windsurf forum.
Met a few others up there who were keen to help as well, great guys.
It's awesome to have this forum, there's certainly some helpful people around here!
Cheers,
Ken.
