Thanks for the answers!!
I also prefer to use the tanking cloak because it "safely" allows me to play recklessly.. I wont switch it anytime soon, even on farm bosses. The tanking meta gem is awesome and I wont throw it away for some DPS boost.
I will try using BB more often on my next raid. As the main tank, I'm flooded with huge Vengeance pools and indeed the BB might perform better.