I think the best thing to look for when comparing models is to remember what your'e using it for: You will be looking at your monitor. If you use your computer a lot, you'll want something nice to look at that's easy on your eyes.
For this reason, I recommend going to a store and looking at monitors. Yes, online is cheaper, but you need to get an idea of what the thing is going to be like when you look at it. Admittedly, it might be hard to select one based upon the resolution of the video source in the store, but it's still worth it IMHO.
Here's some other tips:
- If you're using it for gaming, make sure you get something with good gamma correction/backlight.
- If you're doing serious things with photography, keep color management in mind. Perhaps even get a colorimeter like a Spyder to calibrate your LCD monitor.
- If you're eyes aren't amazing, or they all seem to look the same after awhile, I suggest finding someone with good eyes. In my case, I usually grab my mother (fashion designer, very picky about color and I/O devices, she uses fashion design software very heavily) and have her go with me when I shop. I usually find that my mother picks out monitors that look amazing, last a long time. But they are usually the most expensive at the store. That said, no one ever complains about them in a family of 6 heavy computer users.
- LCDs are designed to look excellent at only one resolution, the native one. Examine your apps/games and determine what resolution you want/need for this, and get an LCD that has that resolution as native
- The higher the resolution the better, usually.
- You want reasonably high response time, although sometimes these are reported incorrectly.
- Some new ones have HDMI ports :)
Lest I make a brand preference, in the past these have been Samsungs. When I picked up an LCD like 2 years ago for school, I got a Samsung as a) it was the cheapest (smallest, though) there, and b) all the stores I went to used them for their POS terminals, they all took a beating and looked great, and c) the picture was very natural. I figured I'd be getting the same quality, and that seemed to be the case. After about 14mos of ownership, a 15lb hacksaw fell on top of it and cut a gouge into the bezel, and it's still okay. I also must admit that I am very happy with my 23" Acer at work, although the out-of-the-box color accuracy wasn't quite as nice and it needs a calibration.
As usual YMMV.