our summer here in the NE USA has been horrific for wind, so i've kited very little. but it's not like i'm sitting on the beach while others with bigger kites are kiting; if anyone is out, i usually am as well. again, that's my point. my 12M w/bigger board (145*46 TT or JL 6' surf) combo has proven to be just as 'efficient' as those monsters. i'm sorry if you can't handle that reality.
I too suffer from our horrific NE USA wind but with quite a different result. I can't count the number of 9-10 kt sessions I've had this summer on my 17m Dyno, joined by my buddy on his 21m Speed 2. He's on a Spleen Door, I'm on a 135x46 TT. We ride, we jump, we stay upwind. There's nobody
else out, including the bantam weight guys on their 12m kites and surfboards. And the reason isn't cause it's no fun cause they can't do tricks or they don't want to ride. The surfboard guys are on the waves or just riding for the fun of it, not doing loops or anything. They're not riding cause they can't.
So, if the guys where you kite can't kite in less wind than you with their LW kites they're doing something wrong. Maybe they just haven't got it dialed. Alternatively, if you can't get any advantage out of the light wind kites vs your 12m then you don't have it dialed either. Or, you don't want to ride cause you're unwilling to change your style a little to accommodate LW riding cause you can't do the same stuff you can in 15 kts or whatever.