Haven't ridden either of these, but they look very similar. It looks like the Trace offers a 9speed rear derailleur, although specs say 8 speed shifters? You'll have to verify that in person, but that's an advantage based on how you ride. Also appears they both have mech disc brakes; if one has hydraulic that may or may not be something you want. Also the Diamondback has slightly wider tires, not sure if you had a tread/width preference, but you may want to decide on things like that if they're that close for you. It's tough to base your decision on how smoothly these shift, since it's likely they haven't been tuned, that said, I give the Diamondback the edge there based on the Deore up front and the 9 speed in the rear (again, verify this) being close in quality to the SRAM X4 on the Fuji.

And if you still can't decide, pick the color you like best. :-) I bought a Giant Roam 2 for the type of riding you'll be doing, and think I made a wise choice in terms of bike style so I won't try and talk you into anything else. Make sure both have a lockout fork, I wouldn't buy a bike that doesn't give you that option, thankfully non-lockouts seem to be getting rare especially on '15s.