My work has had to replace a bunch of Viewsonics that are only a couple of years old, but the Dells have worked great. I have a 30" Dell at home that is quite good, except the gamut is too high so some colors are wrong (avoid high gamut) My parents and brother each have a 20" Dell that has been running well for several years. (one had an issue that was fairly common for IPS monitors at the time where there was was a dark area across the top of the screen that looked like a watermark, so Dell shipped a new monitor and we shipped back the old monitor in that box)
Dells have more adjustable stands, and IMO they have a nicer overall design.
Input lag is hard to measure correctly. In this case where there is less than a frame of difference between two choices, I wouldn't worry about it... it may even be a testing error.
I hope Apple starts using IPS when they switch their laptops to retina displays... it really is much better than TN, though I'll admit I'm pickier than most.