What other theoryes you have - That you can go upwind on a 18m Vegas with a 145x45cm board on a 25 knots?
sure just edge hard you can def ride that combo, well maybe not if you're a tiny fella but if you're a big lad no problem, one reason people don't ride super overpowered is that it's no fun stomping down on the board so hard all day.
airstyle, racing, freestyle, surf, huge air, kiteloops, wakestyle competition all want different kinds of kites
airstyle needs big kites for more hangtime, shape isn't that important
racing needs efficient kites, high AR, goes upwind
freestyle wants stable kites, that makes them boxier
surf wants kites that drift well, this means they are designed not to hindenberg even at max depower -- this is not a shape thing but a performance characteristic, lots of different designs work here but they have to respond well at max depower
kiteloops and wakestyle competition both want c kites, because of how the kite loads up in a turn or loop and drives forward into the wind window
High ar is only important in some style of riding, in particular for racing you need that efficiency.
I must admit, that i'm neither a technical dude, nor a skilled airstyler, and maybe this discussion is over, but hear is my humble opinion:
1., It's is very interesting maybe only for me, that some here and there brand rep. are silent, in this important quastion!
2., The most reliable explanation which i"ve found is here: http://switchkites.com/blogs/does-aspec ... te-choice/
3., My own poor experiment shows too that big kite, small board is the best combination. With my low aspect pounch 10,5 over 20 knots i have a lot of hang time, and ultra soft landings with minimal bar movement (from 11 to 13 or opposite)