I'm afraid there isn't an absolute correct answer here, but I will try to provide commentary around each point from mine and many friends experiences:
Experience - this is heavily dependant on office far more than region. Offices have different cultures, industries, levels of travel, etc. For instance in Europe Scandinavian and UK offices have more relaxed culture and better hours, and southern offices in the US tend to be similar. Client types is very dependant on local industries (UK is finance heavly, Germany industrial heavy, etc.). I have personally ofund US consultants travel more, but this is just in my experience and can't guarantee by firm
Promotion - MBB typically have a slightly quicker path to partner (again in my experience), but I really wouldn't use this as a decision cirteria. Consulting has very fast progressions, and a 6 month delay really has no influence on your wider career
Earnings - US consulting salaries are much higher than Europe, MBB salaries increase at a much faster rate than tier 2 firms. If you have offers from both you should be able to see exactly how these two trends interact, but needless to say Bain charges clients higher fee's, and this money goes somewhere...
Exit Ops - I have found brand matters far more than location regarding exit ops. Especially in the US/Europe, MBB has a real premium over the market. Office will also have an influence, with SF, London, Paris and New York all especially well regarded offices
I would encourage you to consider what you want out of consulting before making a decision. Is it a two year stint to fast track your career or a path to partnership? What industries interest you most - this inflences how sensible different locations and firms are? Finally, don't underestimate the challenges of moving across the world - if you really prefer living in one place to the other you will probably enjoy wokring there more aswell
Hope this helps