Possibly the wrong (or loaded) question from the OP. I have and will always support Wednesday, my only team. However, I watch a lot of football cos I love it and I take sides/favour some teams over others cos it makes it more interesting. This is not random thing, as I am 60 odd now and growing up forged a few links.
Man U over City - grew up watching Best, Charlton and Law, and remember the European Cup win over Benfica, 68 was it?. City got us relegated from the first division, even though they tried their best not to!
Liverpool over Everton - grew up watching Liverpool in the 70's European games when there was not a lot of footy on telly, had a reyt team and great players (not over fond of fans though) Everton beat us in 66, that's enough for me
Tottenham over Arsenal. Loved watching Ardillies, Villa, Waddle and Hoddle among others. Don't really need to comment on Arsenal do I?
Don't like Chelsea in any way shape or form, so Arsenal and Tottenham to beat them.
Real Madrid over Barca - not sure why, another 60's 70's European thingy maybe?
Stranrear - Used to go on Holiday there.
Think that's it, all other teams it depends on how I feel on the day or what's at stake, usually go for the underdog.