I eventually went with the Dell Ultrasharp. Seemed like the best choice at the time, factory calibrated, if there was something wrong with it they would bring one to replace it at the same time they collected it.
The Asus model did look better for gaming overall, faster response, but I was concerned there was a chance that even if 1 pixel didn't work as intended, It would drive me crazy. Asus do have a return policy for bright pixels on some models, including their 29" 21:9, but the Dell customer service trumped them.
LG's customer service is similar to Dell's, they will pick up your monitor and once they have it back at theirs, deliver one out personally. They have done this for me a few times even when a monitor was out of its "official" warranty period, but I wasn't sure this would apply to dead/fixed pixels and I wanted to try a Dell this time around. There was also the issue that their main model needed a firmware update (1.25) to really shine, and although they would upgrade it for free if you did get one that wasn't up to date, the hassle of getting the engineer round to do so detracted slightly from my overall decision.
I expect by now, all of their monitors that shops have in stock will already be at 1.25 or higher.
I was very impressed with the Dell. No problems
personally with the difference in response time/input lag compared to the others. Factory calibration really does make certain scenes shine as intended, no need for extra equipment. Initial backlight bleed in one corner has disappeared completely.
TFCentral do some very in depth reviews, and at one point had a good roundup of the available models from a variety of manufacturers, although I can't seem to find it now.
http://www.tftcentral.co.uk/reviews/dell_u2913wm.htm
They also have a helpful
selection questionnaire.