The same as bitmap vs vector fonts everywhere else.

Bitmap fonts
Pro:
Free to customize effects in the bitmap
Predefined and predictable
Con:
4 color channels used (4x memory space use)
Must have all potential glyphs exported
Dynamic fonts
Pro:
8 bit alpha used ( less memory)
Generated run time from ttf - has all glyphs from that ttf. (localization ++)
Only uses the glyphs you request
Con:
Limited effects on the labels