No idea if much has changed since my blog post, but at the time the prices for the Dell and Asus were very similar. It was a bit of a coin flip but the Asus was newer and had that premium feel from that come from no Dell logo.
Long term, I've no regrets on going wide gamut. Never used the sRGB mode. 16:10 I'd say is essential, I'd go squarer if I could. Occasionally I'll rotate the screen 90% to really enjoy a portrait format shot, but generally 1200 px high is just about enough. Matt screen and IPS are essential I'd say, deep blacks suffer slightly compared to a glossy TFT but everything else is superior.
I suspect £225 for the Dell would be a great deal, even if it is an old model now. I paid nearer £400.
The Asus came with a calibration certificate, and I saw very little change when it was calibrated. You'll need to turn the brightness WAY DOWN though - mine is at 16 or 17 of 100.