I bought an OPR CK12 that showed up yesterday. I had a Beesneez aluminum CK12 in an Ela M 251 build that is meant to be primarily a vocal mic. I haven't measured anything, but I did a quick test last night. I also have two TC CT12s, a Beesneez gold CK12 from 2016 that was overly bright (aluminum was the replacement) but I only directly compared the OPR and Alu BN last night. My completely subjective findings:
The BN Alu CK12 has incredible low frequency translation and has the most of the "3D" CK12 effect of all the capsules I have. Higher frequencies tend to sound more surgical, or mechanical than mids/lows. I don't care for its sibilance and its hyped high frequencies reach lower than OPR/TC, making it a much brighter sounding capsule. It is an incredible capsule, but I needed to install a plate filter to use it as a vocal mic. I plan to design a different circuit for this one, likely a cathode follower.
I had hopes of the OPR CK12 being the best suited for a vocal mic out of currently CK12s. When I powered it up, I instantly loved it and wondered if it was confirmation bias. I had to walk away, and come back because I wasn't trusting my ears. I listened again in the morning, and I'm pretty certain I now have the best vocal mic I'll ever get to hear in my life. It has such nice hyped highs without being sibilant. Someone posted earlier in this thread that they found it warmer than other CK12s, which I agree with, but it doesn't sound dark.
This is just my first impressions, but so far, wow. I'm really looking forward to trying it on more sources.