IMO, it has to be Warwick. It is above Surrey in the league tables, has the greater reputation, the only multi-faculty institution aside from the universities of Oxford and Cambridge to have never been ranked outside of the top and is the top target for graduate employers. The lecturers and the tutorial sessions are very helpful. Surrey is a good university, but Warwick is the more all round university. I strongly advise you to visit both unversities before making a decision.