This is a difficult question because it is really down to you as a person and where you feel most comfortable.
I applied for all of the Big 4 and I just felt like KPMG suited me best - all the people I met at recruitment events, at careers fairs and so on, I got on really well with, and I didn't feel this was the same with other firms. Everyone I have encountered at KPMG is similar to me, and we all have a great rapport, and I think that really helps in the day to day job!
KPMG seek to employ similar people, and because of this we all get on really well, and socialise outside of work hours. There are always social events or drinks after work or over the weekend.
On a more personal level, KPMG give each employee half a day a month to do CSR work such as volunteering in the community. I don't know how much time other firms give to this sort of thing, but it allows you to develop personally outside of the normal day-to-day role. This is great and means you can get involved in things you really care about - a big group of us at work are currently taking part in the Princes Trust Million Makers Challenge, and we have time to be able to do this along side our jobs!
KPMG has a great professional qualification team who help you in your training, and I have found this to be really helpful with my studies. I'd also say that in terms of personal development on the job, because we all get on well, people are really willing to go out of their way to help you and teach you how to do aspects of the audit you haven't encountered before. This is really important for our job and makes a huge difference to what we do!
Thank you for your feedback!