it depends really what you ride, Freight Train is more downhill than DM, and DM is more like a iguess you would call a bike park trail. The only slightly hard bit in DM is the step up after the drop, first run down that caught me out and i mega cased it, second run i was fine.
The trails are designed to not be overly difficult. I'd say Dirt Merchant is harder than Freight Train, because I can't think of a single mandatory drop (or gap for that matter) on Freight Train, and Dirt Merchant has that 3 footer before the Step Up.