I'd go for shared if I were you. I remember when I was choosing accommodation for my 1st year, I was favouring ensuite myself (although I was given shared in the end haha). But looking back, I think its pointless having ensuite, because think about it this way, you'll almost certainly have to live in a shared flat/house when you move out for your 2nd and 3rd year, and it will most likely not have ensuite rooms. So why bothered getting yourself all comfortable for just one year? and think of the money you'd save.
Its better to get used to sharing a bathroom with other people sooner rather than later.