E.T.
I can't give you any real answers on the MB, although I have an online friend who has one and loves it. The Bob, though - I'm an expert. Yes - the Duallie fits through regular doors. I routinely rolled it right through my single front door and into our entry to get out of the wind or rain. I found one door in a store it didn't fit through, and that was a building built in the 30s. I even used it while shopping at Target - because it turned so smoothly, I could push the Bob through the clothes department and not get caught on the racks. I loved it. My husband ran marathons pushing our girls in it. He loved it.
Last word on the Bob - when you're done you can resell it. I purchased mine for $480 at the REI yearly sale in 2008 and resold it for $350 this spring. So I basically paid $130 for three years of stroller.