MSD makes very good stuff. Haven't used their cops, the gains are minimal unless you get into forced induction or heavier shots of smack, but I've used their ignitions, coils, wires, etc and all are very well made and took a ton of abuse. If I ever need to replace cops I'll go MSD unless I come across something very convincing to make me pick a different brand. The other popular ones are granatelli, whose quality is suspect on a lot of things, and accel, whose ignition products have never impressed me much compared to MSD
The artist formerly known as SteedaMatt.