Frame quality I doubt there is any real difference between any of the big names. How it fits you and feels to you is a different thing, and while I prefer the 27.5 but that also is as much personal preference for where and how you ride as anything else. I also prefer hydraulic disc over mechanical so if the price was the same I would lean toward the Merida, but they both should work fine. Then there is the Giant Revel 29er, it has about the same components as the Rockhopper 29 for a bit less.