DD is in Catered Halls at Exeter - Birks Grange Village. The rooms are really nice, she has her own en-suite shower. The main drawback of Birks Grange Village is the morning walk up 'Cardiac Hill'. There are also Self-Catered rooms in other blocks, which I believe are of a similar standard. It seems a really nice Hall, lots of people and very friendly.
I've been to Exeter a few times for open/offer days (as DD1 also looked at it), and so have also seen Pennsylvania Court and Holland Hall - both catered and nicely decorated. Holland Hall is the most expensive and consequently has a reputation for having some very wealthy students. We also saw the new Lafrowda blocks, which are self-catered and very nice, and I think all had en-suite showers.
The old Lafrowda building (Lafrowda standard?) we didn't like at all as the corridors were narrow and I think the walls were grey bricks, so it felt a bit claustrophobic. These will be the cheaper self-catered with shared bathrooms.
Mardon Hall I haven't seen, but is supposed to be nice. It uses Holland Hall dining facilities, and is an older building with some character I think.
At open/offer days, they typically only open a few of the Halls, usually Holland Hall and/or Lafrowda are open. We only saw inside Birks Grange Village on moving in day.
DD's friend was looking at Exeter as a reserve, and was advised that the previous year most students had got on campus rooms - many in Birks Grange Village as it is quite large and some are put off by the Hill. There is also scope to move halls if you don't like the one you end up in. One room on DD's corridor was empty when she started, and then filled by the friend of someone else on her corridor. Some students will also drop out during the first term.