Well, the Baffin Snow Monster arrived today. Wow, is all I can say. More comfortable than any other outdoor boot I've ever worn. I will give a more comprehensive report after having worn them out a few times.
A few thoughts. The Snow Monster connected to my leg much more than the Selkirk. In bitterly cold or snow squall situations, I'm thinking the two buckle/straps of the Selkirk might be an advantage. That said, the SM hugs my leg without gaps and feels far more comfortable. I can lace it up so that all of the boot hugs my leg not just the points where the straps are with the Selkirk.
I will keep an open mind and put both through the paces but I'm suspecting at this point, and much to my surprise, there are few reasons not to choose the SM over the Selkirk. I'll report back.