I am having a similar U1 vs. 12 debate with myself at the moment. The U1s are more frequent, which is a plus, but everyone seems to get them and I'm going to be living at the top of Kenilworth Rd and so I'm thinking that maybe the 12s are less likely to go past in the mornings full up without stopping than the U1s? But I'm a research student so won't necessarily need to be on campus for a certain time in the morning, so maybe that doesn't matter so much? Hmmm tricky...