I've not used Buck's heat treated 12C27 but have about the same amount experience with Buck's 420HC and 12C27 from both Opinel and Mora. I can't tell the difference.
I have a few knives by Case from their Tru-Sharp stainless, which is 420HC, but unlike Buck, Opinel and Mora who all take their 420HC or 12C27 to the 58Rc range, Case only takes their 420HC to 56 Rc. My Case knives seem to lose their edge faster than my Bucks, Opinels and Moras.
Based on all of this, I would trust Buck's 12C27 in a heart beat but I wouldn't expect it to be a significant, or even noticeable difference.
In contrast, I can notice a very big difference with Bucks old 440C.