Which would you pick between these 2 and why?

As you've already noted, but, perhaps have underappreciated "other associated components contribute in a big way". With that said, as far a preference for "lots of detail but at the same time not the grain" I think the McCormack might edge out the Bryston. I would still choose the Bryston over the McCormack with certain speakers, and visa/versa.

The McCormack has finesse I feel that the Bryston lacks. I always felt my DNA-1 delivered music that flowed. Easy to listen to & smooth. My experience with Bryston - a good amp- left with a feeling of a slightly harder edge and a bit more in your face.

As stated previously associate gear makes a world difference and the other components in the systems I listen to were different.

.02

With most speakers, I'd opt for the McCormack DNA-125 -- I owned one a long while and it's one of those components that I wonder why I was ever crazy enough to sell. Works very well with a nice tube preamp.

I bought the DNA-125 in the end. It's driven by a Spectral preamp and it sounds much better than the Bryston, of which I have owned several models.
While the Bryston is very detailed, to me it lacks character. It's very honest but no soul to it, no warmth at all and in a lot of cases a little thin.
This is the first McCormack power amp I have owned and I am quite impressed with it.
Thanks for all your opinions!

Good choice.