Frame animation or motion/shape animation?

I know that motion/shape animations cause less lags then frame-by-frame animation, I’m making a game and I think the speed of the Flash Player is very important.
is it better to make all the motions in Flash, then play it directly or export the animation into .gif file and import them in Flash again(in order to make frame-by-frame animation)? Because the second way has a huge(I think) advantage: when you set the quality of the movie to low, the graphics’ quality doesn’t change for real since they’re gif