Between a well built suspension hybrid like a Specialized Crosstrail, or Trek DS and a hardtail mtb 29er?
OK, so the tires are a bit wider but that's easily fixed. Frame strength? Wheels?
I suspect that an experienced rider can go virtually anywhere on a hybrid. that a 29er can.
I know I'm not sophisticated about such things but it seems to me that the only things different are visors on helmets and baggy shorts.