Avoid the Metrolink if you can. It can get seriously packed and not particularly nice, and the scrum after the game is horrendous.
Alternatively, if you're in Manc city centre just get a cab to OT or the Lowry (some ok bars there), and if you can order one for after the game, even better. Google a few local cab numbers use them rather than a black cab, much cheaper. Or as others have said, just walk into Manc from OT - it's not that far.
Me and my team get a couple of minibuses there and order them for the way home. Can be tricky finding them after the game but well worth it, and normally back in time for a few to finish the night off.