Well, this is an interesting question, here is my 2 cents:-
I've met both MBS and WBS adcoms here in Dubai. both schools are really near to each other in ranking and both are triple accredited. However, MBS has one of its global centers in Dubai so I was interested to join it, but I changed my mind after I attended one of Manchester MBA events- the event was poorly organized and the dean of Business school focused on Manchester as university rather than the business school! He talked about Manchester United soccer team! but didn't really touch the career of MBA Alums and how MBS would shape it during this financial crises!
All in all, I felt it's pretty much like paying money to get good education from a good BS rather than getting an MBA and find a job that moves your career to next level!
Warwick alums on the other hand seem to be more proud of their business school, although WBS has declined in ranking last year and this year I guess, but regardless, it's always been one of the best 5 in UK- Also I've heard that Warwick online support is way better than Manchester's- not very sure how accurate this info is since I didn't try any of them! One drawback of Warwick is that it's not very well known outside UK- it's like when you talk about Kellogg outside US- people though you're talking about food
Having said that, I decided to postpone my MBA plans as I see many top notch BS lunching online programs- and I expect schools like Stanford, Berkley and LBS to follow the same approach soon.