Mark me down for the less expensive option. Inexpensive bikes from reputable sellers that will back up their sale and have competent (in my experience) are likely to work perfectly mechanically, very fun to ride, and be as fittable as any other.
I don't have a Coop branded bike but have a couple of $1K Salsa sold by REI in the family. They are both the least expensive in that line up: Journeyer with Shimano Claris 2X8 and Microshift Advent 9, pretty much the bottom of those two lines. We have absolutely no complaints about the shifting and mechanical disc brakes. They were inexpensive but are fun and do anything we need them to on mixed surface roads and non-technical trail riding. No hesitation recommending inexpensive bikes from reputable sellers.