The main issue my daughter had at Sussex was the cost vs quality of the accommodation, Some of the older blocks (East Slope and Park Village aren't pretty) the newer ones are nice but more expensive than equivalent blocks at say Lancaster
However it is a still a definite possibility due to the physics department feel and research.
So look at the course composition that each offer (labs, projects, optionals research)
Tough choice, and really I am sure you will do fine at whichever you choose