I was in a similar situation in that I had two offering agents (around the same time). Both wanted revisions, although agent 1's seemed more extensive. Agent 1 did not offer "official representation" at the time while Agent 2 did. After realizing that a contract offered neither of us much "real" protection (since it can be broken at any time by either party etc.) and after much consideration I went with Agent 1 - which included agreeing to work exclusively with him on the revisions.
The agent an I have just together finished the revisions (2 full and quite significant passes, and one small pass that I'm turning in next week) and I cannot express how much better the book is. Perhaps Agent 2 would have also been able to help me bring the novel to this level, but I don't have any regrets about the decision I made. Who knows if the book will actually sell, but I've got my agent (a dream agent) and will be "officially represented" any minute now and I've got a book that is so much stronger than what I had 9 months ago.
I'm not going to say it's not a risk working with an agent that requires revisions...there is definitely a chance they won't rep you at the end of the process, but if you think the notes are good, I say take that chance, the odds are you'll end up with a better book, even if for whatever reason you don't end up working with the agent that helped you get there. I will also say that the 9 months I spent working with my agent helped me figure out if he is the right agent for me, before we even go out on submission - which is great. Basically there was no wasted time...it was all a great learning experience.
Additionally, I read a great account online by a published YA author about her first publishing experience. She had queried a book and gotten response from a great agent that was interested but wanted to work on revisions with her exclusively. At the same time she also got an offer of representation, no revisions needed. She took the no revisions offer. The book went out with no major changes and the book never sold. A year later she and the agent parted amicably. She queried another book she had written in the meantime and the same agent that suggested revisions on her first book responded again, with the same basic idea - "I love this, but it needs revision." This time she went with that agent, realizing that maybe she needed help bringing the book up to a level that would be sold.
She spent the better part of a year on her revisions but then she and the agent signed and when they finally went on sub the book sold FAST with a major three book deal.
Does this happen to everyone? No. And you should definitely only make the decision you're most comfortable with...but I have to say, having been through the revisions (hellish though they were) I wouldn't go back and change a thing. Talk to each agent, try to feel them out personality wise, try to suss out what revisions, if any are necessary with agent 2, and then just go with your gut. Try to ignore the pressing feeling of it needing to happen fast...sometimes it taking longer is a good thing.
Good luck with whatever you decide!
eta: this was way too long! sorry!