Monitor Comparison

I am in the market for a new monitor and I would like some help choosing between the 2. I am down to choosing between 2 monitors.

this dell monitor

a 22 inch dell with a resolution of 1680*1050
contrast ratio 1000:1
5ms response time
no webcam

http://accessories.us.dell.com/sna [...] u=320-6107

and this monitor

a 20 inch dell monitor with a resolution of 1680*1050
contrast ratio 2000:1
2ms response time
integrated webcam

http://accessories.us.dell.com/sna [...] u=320-6964

I play mostly first person shooters and real time strategy games and I don't want to get a display with a higher resolution than this because I don't want to loose performance.

My main question are how noticable is the contrast ratio difference, the response time difference, and the screen size.

Your suggestion on which would be better are appreciated.

Thanks for the help in advance.