What kind of a mountain bike do you have now? With slick tires and few other cheap changes, old mountain bikes can be great all-around/commuter bikes. If you do the cheap changes to the existing bike, that would get you on the road and building your fitness back up. It think it might also help you in deciding what kind of new bike you wanted. Could you post some pictures of the bike you have now?

The three bikes that you mentioned are look like 29r mountain bikes --- essentially mountain bike with 700c wheels.

You didn't mention a budget, which would certainly effect the recommendations folks might make.