M.F.
I don't know anything about the Mountain Buggy or the Quinny, but I really enjoy our BOB double stroller. It is so easy to use - feels like I am pushing practically nothing. Very comfortable for the kids. It also can be used with or without the wheel locked. I finally settled on the BOB because it allowed for the tallest kid - so I can use it a bit longer than the others. Purchasing it on sale was still pricey, so being able to use it a bit longer was appealing. You have to order the water bottle holder separately - it was worth it. Hope this helps. Enjoy your excercising! : )