theyre fairly interchangeable and on a daytrip the surrounding countryside is not really relevant. both have good museums though, good gardens and good buildings that are really old. oxford is marred by all those mean little houses around it. both are marred by young succesful people with rosy cheeks and a future of huge economic reward ahead of them. oxford has better pubs i think, from what i can remember. but cambridge is certainly prettier and i prefer the atmosphere.