The fps people will probably say... lower is better, get that one.
However if you google "5ms vs 2ms for gameing", you run into stuff like:
Do not look at response time when purchasing an LCD!!. It means nothing. Actual total response numbers are much higher than advertised
Response time is a misleading sales gimmick.
ms = miliseconds = 10^-3
so 8 ms = 8*10^-3 = 8/1000
so 80 fps gives is 80*0,008 = 0,64
so theoretical loss of 0,64 frames. But monitors often only run 60Hz so it doesn't matter as much. And like said above. Response time is a misleading sales gimmick.
Reviews and first hand experience is the way to go. So many subjective opinions considering colours and such.
Most monitors rated around 5ms have an actual total average response time between 20-40ms.
Remember total respone time is what matters, not its 2 or 5ms responce time.
Find a monitor with low lag input (usually this part isnt advertised by people selling the monitors, but its more important overall).
here review site for monitors:
http://www.prad.de/en/index.html
Go read up on the monitors within your pricerange, and pick one with the best review/bench whatever.
If you play fast action FPS's (Q3A) you may notice it. But in my experience, 5ms is fine. I have used a 1ms ViewSonic before, and it was super smooth though. I could tell the difference from my normal 5ms gaming monitor.
5ms while playing at 80fps means a loss of ~0.4 frames pr sec.
If you noticed any differnce, it probably wasnt because of the responce time, but something thats more noticeable like lag input.