Brakes can be your friend, or your enemy if not set-up correctly.  Different riding styles also require different types of brakes.  Like road type feel with modulation?  Go with a standard Canti style brake like the Shimano or TRP  950.  Want pure power and mud clearance?  Go with  Euro style brakes like the Spooky, TRP or FSA.

Avid Shorty 4 & 6	Shimano R550	TRP Carbon
Spooky	TRP Euro X	TRP Euro X Carbon
FSA SLK	Cane Creek SCX 5