The last time I heard either an 11 or 12's was at least 5 years ago. It was the 12's. I can only go by memory. Taking that into consideration, I would rate them about the same, as far as warmth goes. Understand, though, that's my best guess.
I can tell you, for sure, the PV12 is warmer sounding than the 16. For me, its way too much of a good thing. It borders on dull sounding. Its the kind of preamp you buy if you need to "fix" something.
In your OP you say that you don't want a hard/bright treble. You may want to have a look at your CD player. If thats the real problem, I suggest you go there first. All these vintage CJ components we are talking about here are warm sounding almost to a fault. If you set all this up and then change your CD player, you may not like the system.