Re: Mountain or Cruise?
I would go with the Rockhopper, as it's frame and components would no doubt be higher quality than any Walmart bike.
However, I would advise you do more homework to make sure the Rockhopper can fit the HS and 4G without any clearance problems. You're going with, IMO, a great drivetrain, but it's nowhere near as compact as a typical 2-stroke setup. Specifically, engine height can be a problem.
My HS and 4G measures roughly 9"L, 9.5"H, 9.5"W. Yours will be 1.5" wider since you're using the regular 4G, not the narrower Honda-style one that I have.