One of my sons attended the Oxford campus and the belief there was that Oxford was harder. No idea if that’s true. A negative for many people is that Oxford is super quiet, with no place in easy walking distance. On the other hand, being part of a college team can be a phenomenal experience. (Due to the camaraderie and structure-- it can be something you look back fondly on for the rest of your life!)
So – only you can know how to weight the various factors. What a nice choice to have!