OCZ yes, Corsair no. I have Corsair XMS Pro - which i got through a deal, i wouldnt normally have gotten it - and it doesnt overclock nearly as well as the competiton. G. Skill is the best stuff on the market IMO, and OCZ is close behind
Corsair has only one good line, Valueselect lol. I have it and it doses awesome. If you add voltage to the ram you can tighten those timings even though if you OC youll have to put them back because you cant really tell the difference.