Well I can back Samsung, but Viewsonic LCD's tend to die very quickly, I know you are talking performance, but every time I buy a Viewsonic, it dies in a year to year and a half. They all died from blown capacitors.

Someone told me on DigitalVersus they tested the Viewsonic vs. Samsung
The Viewsonics have a lower input lag
but just by 1frame..is that 1 frame important enough for an FPS gamer to pull the trigger?

Or will the better contrast ratio make me a happy camper?

120Hz you probibly want a solid 60 fps, bare minimum 30 solid all the time, with 120fps being ideal, the reason I say this is because there is no point going to a screen with 1 frame every ~8ms, and then have a card giving it a frame every 32. It is a little bit like buying a ferrari, and running it on remoulded tyres :P

This is of course based on ideal circumstances. If you are getting a 120Hz screen for reduction of motion blur, and because they have such a low response time and input lag anyway, then as long as the FPS is smooth then it shouldn't matter. If you are not happy @ 60Hz because you don't think it is fast enough, on a CRT (with in theory 0 input lag), I don't think a card that will give any less than 60 fps will impress you.

http://www.lesnumeriques.com/article-312-6749-41.html
My faved (french) hardware reviewing site says: both are very close, the ViewSonic has even better "reactivity" (not just response time, but input lag + image "trail") although the difference is probably impossible to notice. More importantly, it has better colors. All in all both are very similar but the VS gains the edge over the slightly older Samsung, so I'd go for that one.