You indeed have done your homework. I would stay away from the bike with the suspension fork. You don't need a fork for the type of off road riding you describe. The Jamis and the Trek have nearly identical specs: 9 speed, same gears, hydraulic disc brakes (not sure which brand is better), both have 32mm tires. The big difference is that the Jamis is steel and the Trek is aluminum. Slim would tell you that aluminum wears out after three rides and steel will last until the next apocalypse. I think either one is fine and I would not be surprised if 95% of the bikes out there are aluminum. There is one difference, however. Steel rusts. If you live and ride in a really rainy area, perhaps you will be better served with aluminum. Steel supposedly gives a smoother ride. YMMV.