depends on the cost imo, honestly you can probably find a benchmark or something like that if you hit up google. I'm sure somebody out there has tested 2ms vs 3ms vs 5ms etc.
My opinion, is that if you are a gamer then go with 2ms, simply because you know that you're getting the best, I have gone with 2ms lcd panels for my last THREE lcd purchases. I am sure alot of people will tell you that 5ms is fine for gaming and im sure it is, but if its not alot more money, get the 2 ms.