Choosing a University is a hugely personal, subjective decision. There will be factors which are critical to you, which are less important to others, and vice versa. This is as much about choosing a city that you prefer, as the university or faculty itself. If you are happy where you are studying, you are more likely to do well: that will have more of an influencing factor than, say, the quality of an individual lecturer.
Ignore those who may jump on this thread and point to small differences in the league tables.
Make a list of all the factors that are important to you e.g., nightlife, cost of living, access to societies, proximity to the things you like doing etc. Assess each of your choices against those. Don't ignore your gut feeling/instinct based on your perceptions when you visited each Uni. Take with a pinch of salt the advice of others (particularly those who don't live and study in any of the places you're considering).
At the risk of being facetious, this is a bit like if you had said "I'm thinking of going on holiday to France, Spain or Italy. Which is best?". Without knowing what you love doing, or what you want out of your holiday, other people's views are naturally skewed by what they enjoy, not you.