I am an Edinburgh graduate and I loved my time there. However I have also visited UCL and knew several happy students there and thought it was a great college with a really vibrant atmosphere. I think it really depends on the individual and the course you want to study. I knew a couple of people who studied psychology at Edinburgh and they enjoyed it and there is an active psychology society.
I think that in terms of reputation there is little to choose between the two (in fact I think that in the current job market employers are more interested in the individual rather than the specific university) and that perhaps you should visit both during term time and then just go with your gut instinct.