I'm using a VX2025wm with the Xbox 360. It does not have pixel matching meaning that it will stretch any non-widescreen input to fill the entire screen instead of adding black bars on the sides.

This is not an issue with the Xbox 360 as the video signal is in widescreen. Possible problems if you use it for PC gaming and the game does not support widescreen. However, you can always enable pixel matching using your video game drivers. From what I have read from the [H]ardForums (probably the same place where Google sent you), there are issues with 7900 users as it seems the pixel matching cannot be switched on.

If you only want to use the VX2025wm with the Xbox 360 then it's not a problem. If you want to use it with your PC as well, you are ok as well unless you happen to use a 7900 video card.

If you only wish to use the Viewsonic with the Xbox 360 and save some money, the VA1912wb is probably fine. But if you wish to use it with your PC as well, I'll advise to get the VX2025wm as it has higher resolution, higher contrast and DVI input for better looking text.