It all really depends on what your willing to sacrifice.
Gilwell is the cheapest - (and when you start, all the rooms will have been refurbished (getting done over the summer) It's really sociable, but you don't get en suite, and if you are on floor 7 - 8, your kitchen is a lot smaller than lower down flats because of sloping roofs. And if you lose your door key, it's the cheapest halls to get it replaced in. £25 instead of around £80.
Francis Drake/ Mary Newman - both brand new, both very expensive.
Robbins - Big Rooms, Ensuite - though don't choose if you dislike climbing stairs, there are alot.
Radnor/Pilgrim - Ensuite Pretty much the same really.
The problem that plymouth has in comparison to other uni's is that most halls, don't have a communal space, with sofas and the like. (Gilwell doesn't even have a dining table).
If that's a problem, there's always the Unite Buildings, St Thomas Court, and St Teresas. Privately run Halls of Residence
I was in Gilwell 1st Year, and am moving into Robbins to be a Resident Assistant in my 3rd year.
The "curfew" in place is is just a keep the noise down after 11. But if your having a party, clubs and pubs are minutes away.