Giga:
Pros - Higher sample resolution, more voices, greater potential storage, faster load times, high quality libraries
Cons - Can be unstable or unreliable, needs extras like controller, interfaces, and computer.
MPC:
Pros- Portable, rock solid performance, built in controller, insanely huge library, groove templates
Cons- Old technology, slow load times, limited sequencing compared to DAW.
If anyone can think of more, feel free.