Hi! I also have an offer from Manchester for the same course and I’m toying with making it my firm.
I’m from Devon and after visiting Manchester earlier in the year, I found Manchester to be cheaper generally. A lot of people from here describe it as ‘near-London prices on not-London wages!’
That said, Exeter is close to quieter areas when you want to get away but still don’t want to be totally isolated, and you can get there on a train (Teignmouth, Dawlish, Newton Abbot and Torquay are all quieter than Exeter and have parks and/or beaches.)
Remember you don’t have to firm & insure unis until June, so there might be a lightbulb moment where you realise which one is perfect for you 😁