Its really difficult to say - for some people lakeside is dream accomodation, for others its a complete nightmare.
Do you want social life? Do you want it not to be ridiculously expensive? Do you want to be close to the business school? There's no 'best' accomodation... just whats best suited to you.
For me, I would choose none of the ensuites but thats because they're generally a lot quieter than the rest. JM is probs a good bet, though for a few pounds a week more you get AV which is overall much nicer accomodation with its own common room and launderette in the building. Downside is that its even more quiet than JM (and JM sometimes has a rep for being really quiet). Lakeside is like a cemetary.