From personnel experience in applying to the RAF as pilot whilst at uni, they really don't mind what degree you're doing. However, I'm doing aeronautical engineering, and all the other pilot bursars on my course do really end up hating the course purely for the fact that they could be doing an easier one, but will have the same end job result. I'm not saying pick an easy one because it's easy, but pick one that as people above have said, you enjoy. Don't do a technical one because you think it's what the RAF wants in a pilot.