I was stuck between both of these unis last year, although I had offers for English Lit, so I can't really comment on the two courses you're choosing between. I ended up insurance-ing Leeds because I just really disliked the general atmosphere and location of Sheffield, whereas I thought Leeds' campus was lovely, although there are undoubtedly lots of people who love Sheffield and hate Leeds. I've spent quite a lot of time in Leeds over the past term visiting people (so I'm probably a bit biased in favour of it now, since I know it better than I know Sheffield), and all the students I've met have been really nice and friendly, so I don't think that you should be put off by the 'kind' of person that is at Leeds. Leeds is a big university, and the student population seems very diverse, so I'm sure you'd be able to meet lots of people you get on with.