Both are excellent. The vast majority of people would be served well by either.
With that said I find that BCM has an edge on reliability and durability.
Early Noveskes had CMT carriers where once in a while a carrier key would come lose, mine was one of these. This was a sample of one. I have three BCMs with more than 3 times the rounds through them combined vs. the one Noveske I owned. And I’ve not had a single stoppage (1K rounds through the stainless Noveske and just under 2K rounds combined through the 3 BCMs).
I had a 14.5" Noveske Afghan (stainless bbl).
BCMs I have:
I have are a SS410 16" midlength turned down to .650" behind the gas block.
A 16" non-hammer forged chrome lined BCM midlength.
A pre-production 14.5" hammer forged (BFH) BCM midlength (I’ll report more on this one later, it’s VERY worth the wait!)