UCL or ExeterWatch
I don't know much about them either but the locations are very different so maybe that's a factor? Also, carefully look over the modules at each place, that helped me decide the most.
I cant choose which to put as my insurance choice. At this time with A levels cancelled I can't be sure I'll get the grades to go to my firm choice. I enjoyed both the open days and don't have much to go on when it comes to differing between the two. I know the stereotypes for Exeter but I don't really know anything about UCL and am not sure which to go for - both gave the same offer so that doesn't matter - if anyone knows anything or has a good way to choose please let me know
With regards to other things, it really is up to you. If you would prefer to live in a large cities and like their vibe, I would go London. Exeter at the same time has a large student population for a relatively small city so you will live in more student atmosphere. If you live in Exeter, you have a chance to see rural Devon, take day trips to seaside towns like Exmouth etc. Also keep in mind that life in London is more expensive than in Exeter. That said, London gives a chance to go sports events and other large events.