My opinion might be a little bit bias because I play a lot FPS games but I have used over 10 LCDs including the ones you mentioned. I didn't care too much for the 1704FPT because of the low response time but yes the contrast ratio is higher, however the 2005FPW is amazing, I used that for about 6 months until I got the 2405 which is even better. I don't think you could notice the difference between the 1704FPV and the 2005FPW, even if you could it would be slight and the size factor with the extra res and desktop space seems like it would rule it out as a better option. They all look great and are excellent monitors. In this case though I think bigger is better. The pixel density is 99DPI on the 20" and 96.4DPI on the 17" so they are pretty close with the 2005 having a slight advantage there, then the response time is 12ms on the 2005 vs the 20 or 25ms of the 17"
I don't think you would be unhappy with the 2005.