Pick Soul if you
- Want a kite that is easy to fly.
- That does not backstall easily.
- That behaves like a tube kite.
- That has decent upwind (not great) angles.
- That jumps well (they both do).
- That is very easy to relaunch.
- That is very easy to drift launch
- That is easy to handle in gusty coditions.
Note the phrasing Easy here. It is not better. it is just easier. Both kites can relaunch, drift launch, handle gusts etc.
- If you want better upwind angles
- wider wind range (for average kiter there is no difference. How ever experienced foil kiters will have more range (mainly can handle stronger wind) with higher aspect ratio kite because it flies farther in the wind window generating less pull)
- Jumps even better. Also you can jump a lot more because it goes better upwind.
- turns better (even though it means stalling)
- Tacking inc foot switch is far easier with sonic
- It is harder to use. For me this is actually a plus. Because it needs some work. Using soul is just boring to me.
- It will punish you if you let it to the edge of the wind window especially in gusty conditions
- Slack lines will often lead to bowtie. So you need to be able to keep tension in the lines.
With higher aspect ratio kites you can loop them. However tighter loops dont generate as much power as with soul. So looping sonic is possible but it is trickier. If you stall the kite when looping it does not generate power.
10 knots and 75kg => I would pick 12m (soul) -13m (sonic) kite. Personally in those conditions I (80kg, 800cm2 front wing) use 18m kite, but it is just because I like to jump and love hang time!