What is (based on your experience) is the best 1st Year Undergraduate accommodation in terms of quality, affordability, location, nightlife, etc etc?
I mean in terms of nightlife, most accommodation is on campus so unfortunately involves a bus trip into the city for the clubs in town - unless you are a keen walker. Staying in city accommodation definitely has its benefits as it is short walk back from the few clubs in the town - but requires a bus to campus to make lectures. In terms of the best flat experience I'd opt for the cheaper accommodations - more people per flat so more opportunity to meet someone you like, and better atmosphere due to the sharing nature of the flat e.g. Eastwood. Would have to put a disclaimer about the nightlife though, if you are from a major city, the nature of Baths underground clubs will for sure be an unsatisfactory experience, so get drinking early.
All the accommodation buildings are maintained to a high quality. In terms of location, I think the main choice is whether you'd like campus or city centre accommodation. Bath is a relatively compact campus, so you are within walking distance of all facilities regardless of the accommodation building. Whereas, in the city centre you are in a very convenient place for evening/weekend activities but will need to travel to campus frequently - there is a 24/7 bus route close to the accommodation.
Hope this helps and please do ask if you have any further questions.