Depends on the technique. I'm right-handed, FWIW.
For front kicks, side kicks, round kicks, or back kicks, they are equally good, overall. The right is a bit stronger, the left is a bit faster, but the difference isn't that great.
Left leg is better with the following:
Spinning side kick
Spinning hook kick
Spinning back kick
Sweeps
Right leg is better with the following:
Crescent kick (both types)
Standing hook kick
Spinning crescent kick (both types, whether just spinning or jumping and spinning)
Jumping front kick
Jumping spinning side kick
Even though I can still do all of the above "handed" (footed?) kicks with both legs, there is a good bit more of a noticeable difference when using different legs. I hope to iron out these imbalances one day.
This also carries over to the legwork in some kata, such as Empi / Wanshu, where a 360 degree jump and spin is performed. I can make this jump with no problem, since it goes counter-clockwise. I tried doing this in reverse, and even with much practice, I still can't quite hit it.