Slow down wherefrom?

Hi I`m making a flash game and have finally hit the point where it starts chugging.

I was wondering if anyone could help me out with some knowledge about , well what is the slowest / fastest way of doing things in flash.

The slowdown has occured after I’ve put in a section of tiling animated sprites, 6 frames of .png images per sprite.

Is it faster to animate in flash using tweens etc or to animate using this method (flipbook through sprites) ?

Thanks in advance.