My dad, who is a united fan, used to go to both quite regularly in the 50's and early 60's. He stopped going to Maine Road when he met my mum in the mid-sixties but kept going (sometimes with her) to Old Trafford - I think he's been a season ticket holder for around 50 years now.
He was forced into attending Maine Road again with a greater degree of regularity in the late 70's by his recalcitrant son who for reasons he has never been able to understand decided to support City.
We went to a few interesting game together before I was old enough to go on my own, including the 1981 cup final where he was loudly cheering for City.
The story ends on a sad note, however.
Now we pose a threat to his beloved united he seems to spend nearly every waking hour slagging us off. He now hates us more than Liverpool. If you close your eyes you can actually smell the fear.
God I love being a City fan.