Hi
Congrats on both offers, especially because they're in different subjects (must have been some personal statement!)
I can't really speak for English at Exeter as I do Philosophy and Theology at Durham but I'll give you what I think of Theology at Durham. First things first, I agree with Maisyf1, Durham is a nice, safe town, quite small but has a nice community feel to it and the college system really helps with that. you'll be walking through town seeing lots of people you know in no time!
as for theology at Durham I disagree with the above post as I think the theology department here is great. My first year modules were taught by really enthusiastic and inspiring lecturers that more than made up for the fact that they were compulsory and maybe not always my cup of tea. Since you're in for straight theology you will have a much broader choice as well and won't be restricted either. Pretty much everyone in my year is fond of at least one lecturer (AT LEAST) and, on the whole, the lecturers are held in high regard by a lot of the students. I think Maisyf1 saying one of the worst things about compulsory modules is the fact u have to sign in is scraping the barrel for criticism a little bit (sorry!), as I'd hope that because you love the subject, making it to lectures more than once in a while is probably something you'll do (that IS what we are paying for...)... so don't be put off by that.
The department has always been helpful if you have any problems or worries and lecturers frequently set aside office hour times where you can come and speak to them about essays, exams or general questions that you might have. They are incredibly friendly and understanding.
In terms of results, Durham frequently tops theology tables and I think this is down to the knowledge and teaching of the lecturers (and the fact there is so much support available), but also because the course is made up of friendly and knowledgeable students (but without being competitive!) It is a really nice learning environment (and this coming from a joint honours student who is there only half of the time!) and you will come to see that the theologians are a tight knit bunch.
I hope that was helpful and if you have any questions I'll check back and try and answer them