I have had the U2412M for a while now and also just recently got a 2410 as a second monitor. They are both excellent and I don't think you will be disappointed. I've owned a lot of monitors and the mid-high grade dell monitors are very, very good quality in my opinion. One of the areas where it exceeds that you might not think about is the stand. It's very strong and can move in every direction, plus has a standard square size "socket" where you can click out the stand and add a wall mount (for example if you wanted). I had an LG and a samsung before it and the stands sucked in comparison. Very little room to select the view you want.
Also, the 12 has physical buttons on it which are excellent. The 2410 and my samsung have capacitor type buttons where you have to feel around to get them to light up in order to change anything which is a huge pain. I play xbox on my monitor as well as use it for the computer so I switch between the input frequently. I am not familiar with the asus you are talking about so I'm just giving my 2 cents about the dells.
As for cons, it doesn't have an HDMI port. I'm not sure if the revision you mentioned added one but I don't think so. For me, that was disappointed because my xbox needs HDMI. I really feel like for that price point (somewhere around 350$ msrp) you really SHOULD have one. It's got display port but I found that to be way less convenient. So let me ask you this, do you require HDMI? If you are just going to connect to your PC, it should make no difference but if you want one monitor for all your devices, it might not be the best choice for you.
If you can do without HDMI, you won't be unhappy with the dell. I am very pleased with mine. A side note though, I paid somewhere around 350$ for mine new, but I got the dell 2410 used on ebay for about 150-175$. The bezel on the latter has a few minor scuffs but I would go with that deal over the former. I guess it depends on if you are willing to get it used or not, I did have to send the first one I got off ebay back because it had screen pixel issues but did not have to pay anything. It was just a pain. But in the end, it worked out great. Hope any of that helps in your decision. Good luck.