It sounds sort of cliche, but both of them felt that Irvine was too fake, too made up and lacked character. It really is a planned city, with strict ordinances. One of them had problems with the cost-of-living, which doesn’t help. The other felt that it wasn’t really a campus that had much a community, and wasn’t interested in the greater community around it.
I’ve been out to Irvine a couple of times, having considered a job offer out there. There are cool places to live nearby, but I didn’t find much in the city that was redeemable. I’m pretty biased, though, as the 2 who lived out there have similar tastes in living (well, except Pittsburgh).
I can only talk about the cities, though, but I was in school for 7 years and my experience with grad school is that, all things equal, you should go for the town around it. Especially as a grad student, you’ll want to be able to find some activities away from your constant studying. You’ll go insane if you stay wrapped up 100% in your work.