but you would mostly dunk off 1 foot on fast breaks or when you cut to the basket when you are running, and they both look good.

i suggest training on both leg, you would use both 1-leg and 2-leg dunk or layups at different situations.

__________________
"Look me in the eye. It's ok if you're scared. So am I. But we're scared for different reasons. I'm scared of what I won't become, and you're scared of what I could become. Look at me. I won't let myself end where I started. I won't let myself finish where I began. Look me in the eyes. I have something more important more courage. I have patience. I will become what I know I am."
-- Michael Jordan