I use both 2 and 4 strokes. As a few people have mentioned, neither is better, they are just different. You can use either in ANY plane. However, IMO each has advantages over the other. I use 2's for high-speed planes, and 4's for military and aerobatics. I don't care what ANYBODY says, 4's burn MUCH less fuel than 2's they are 10 times cleaner, and OH THAT SWEET SOUND!!!

Let's face it, wouldn't you cringe to see a Harley-Davidson HOG cruising down the street with a 2-stroke Kawasaki engine screeming along? (Rrrrriiiing-ding-ding-ding-ding)