Are you talking 1200 yamaha vs 1100 yamaha or 1200 yamaha vs 1100 kawi?
1200 yamaha is better and worth the money over the 1100 yamaha. You get carbs, better bottom end (what really matters on a blaster) more bore. Take the 1200, mill the head or go aftermarket, throw some flame arrestors on it and go. The ski will be really nice.
The Kawi 1100 makes more power than both the Yamahas, but, in order to get that power, you need carbs, intake, reeds, head, timing advance and dry out the pipe. If you are looking for easy power, might be more than you want to get into. None of the mods are hard, but they do cost money.
Good luck,
Scottie