I hate Man United. I dislike Man City. Therefore I'm not biased in either club's favour.
Old Trafford is the best stadium I've been to in the UK by a mile.
I've been to every 50,000+ capacity stadium in the UK except Ibrox and Twickenham, and rate OT above all the others.
Don't get me wrong here, I accept it's a matter of opinion rather than fact, but I find OT hard to criticise.
City's ground is a nice facility without a doubt, but the relatively low capacity means it's by no means a super-stadium, and the fact that the stands aren't quite as on top of the pitch as they are at Old Trafford means the atmosphere isn't quite as good as the sound doesn't cascade as much. On saying all that though I do think it's the perfect venue for Magic Weekend. We don't need a 76,000 capacity for that, and the decent facilities at Eastlands combined with Manchester's relatively central location in RL heartland makes it ideal.