The La7 might be a popular plane, but not more so than several others, like the Pony, N1K and Spit IX. If it were so great, wouldn't it finish #1 overall in popularity, or K/D vs fighters? Best it's finished in popularity is 3rd in the last 4 tours, most times it's 4th. The La7 also really doesn't stand out in the stats when you look at K:D vs fighters (thanks to AKDejaVu for all the numbers). It averages about 15-16th overall in any of the last 4 or so tours in K:D, consistently beat out by the 190A8, Ki61, N1K. The plane is good, but it's not very overwhelming it would seem.
The La7 is simply not a balanced aircraft. It's 8 parts defensive speed, and 2 parts offense. Avoiding deaths to La7's isn't that hard, but catching one in order to shoot it down can be. The La7's worst fear is a diving N1K or Spit, force it to turn and slow, then it's easy meat.
-Soda
The Assassins.