I'm looking at getting the Aero Free for winging because of it's reputation for being very "surfy" and having a good low end. I'm an experienced prone shortboarder and want to get into foil surfing eventually but for now just winging with small wind swell. I'm looking at the Aero Free 800 because of my weight (~60 kg) but the aspect ratio is fairly high on that one (7.3) versus a 6.5 for the 1250 cm^2. I'm wondering if that is going to affect the maneuverability. It doesn't make sense to me that it would, because the foil is smaller overall, but would like to hear peoples' experiences. Also need to know if I will eventually want to transition to the 600 fuselage or whether the 680 is sufficiently surfy (since the 600 only compatible with the carbon masts and I am trying to save money).
It sounds like you're overanalysing the specs. AR difference of less than 1 is negligible.
The Free 800 is very loose in roll. Noticeably looser than the Free 1000. Bottom end is not much higher than the Free 1000. It's a fun foil, I don't think you'll regret it.
I wing both the Free 1000 and Free 800 on the 68cm fuse for the same reason (cost) and they are great.
Side note, if you want to play in small wind swell (less than waist high), then the 800 will feel small and a bit too fast. It's good for slightly bigger swell. Still fun, but you need more swell energy compared to the 1000.