Since NM Merriams are my "home turf" birds, I will jump in again on this topic. First of all, the coloration of the Merriams subspecies can vary a bunch, and is not necessarily an indicator of the purity of the birds in a given area. Here in southern NM, you will rarely find a Merriams gobbler with the classic "white and black" coloration that is so often associated with this subspecies. Merriams rump and tail tips will often look very white when alive and from a distance, and turn out to have a buff hue when you are "up close and personal" with a downed gobbler. There are some pretty distinctive color differences in pure Merriams and pure Rios, but they are not necessarily related to the tail and rump coloration.
I agree entirely with you, mmichelli, on your assessment of Merriams and their reputation of being easily called in. It is true that they will gobble more than other subspecies, from my experience, but often those are just "courtesy gobbles". Hard-hunted, public land turkeys, whether they be Merriams, Rios, or any of the subspecies can be maddeningly difficult to call in at times, and laughably easy at others. A general rule, in my opinion, is that the less a gobbler has been hunted, regardless of subspecies, the easier he will be to kill. That's my story,....and I'm stickin' with it!