Flash Vectors or Pictures?

All my tiles in my game are set up with vectors really basic vectors. But, im worring about later on when the games done im probably going to upgrade all the graphics to be higher graphics.

So my question: do vectors cause less lag than bitmaps? Just pretend that each vectored tile would have about 20 lines each.

This is more so a question for my map editor wich shows 400 tiles at one time.