I go to University of Kent and I don't know much about University of Sussex.
So Canterbury gives off a large town vibes more than a city. It has a big campus, and it is on top of a hill. The actual town is at the bottom of the hill. During summer times, the town is really pretty, there are cute picnic areas and the people are quite friendly. It is a 50 min train ride to London St Pancras from Canterbury. I think the university accommodation is quite expensive especially for an en suite. Parkwood Houses are the cheapest and that is shared bathroom between 5 people. Elliot College is definitely not worth it, it looks like a prison cell (I think the architect was someone who designed prisons or it was a prison - not sure). This accommodation is flat with shared bathroom with a kitchenette so a small freezer/fridge shared by I think like 13 people. Off campus there are cheaper accommodation. The library is quite nice, it is 24/7. I really think the societies are quite inclusive and they throw great events. Overall, I loved this location.