I would choose Brasenose. It has some very classic and beautiful buildings and the location is just perfect: right on Radcliff square.
Although Exeter is very beautiful and relatively cheap too, the college can only accommodate 50% of its undergraduates. Still it would be a fine choice if you are not too concerned with it.
Pembroke is very poor and therefore too expensive. I believe their accommodation is the second most expensive around. Their results in the Norrington Table are neither that great.
Christ Church was once one of my favourite colleges, mainly because it was the best known college (how dull). However, when I visited it last summer, it lacked the warm and cosy atmosphere that some other smaller colleges had. Furthermore, like Alexander (who is an Oxford local, so he should know) already said, chch students tend be arrogant and posh. However, since it so big, there are ppl from all sorts of backgrounds.