Have you visited each campus and spent a day in the city?
I found it really helpful to spend a day in the city/campus first to get a feel of what it is like. Could I imagine myself here? What green spaces are nearby? etc.
If you have been to an open day, hopefully, you will have had the chance to talk to current students and ask them more casual questions about their uni experience. If not, then this is definitely something to consider.
I personally love Birmingham. It is still a huge city, but not as overwhelming and pricey as London, and you still feel like part of a student family here. There is lots to do and see, plus it has great connections to just about anywhere in the country. It is very diverse, too, so you get to meet people from different backgrounds.
I have never been to Leeds, so I can't say much about it, but I can imagine it has its perks! Really depends on what you are looking for