I would prefer corsair. I am sure OCZ is a very good ram, I actually use OCZ Rally2 flash drive and PSU on another PC, but for some strange reason, I always had problem with OCZ ram. Once I bought from OCUK, had to Return it because it wasn't stable. Then my friend bought OCZ DDR2 1150MHz model, had problem with it as well. Today I went to one of my clients place to fix PC problems, and find that the OCZ ram was causing trouble. But so many other people are happy with OCZ, maybe it is just me.
I have always used corsair and they never gave me any problems. I am using this at the moment:
http://www.overclockers.co.uk/showproduct.php?prodid=MY-193-CS
I am happy with it. Running it at 7-7-7-20 without problems.
And for the speed, it is always good to go for a higher speed if there is no huge difference in price. It always pay off for the next upgrade.