While I'm a pentode guy & do prefer the pentode Simuls to the Triode Simuls, IMO no Simul has the speed & bark of a full pentode A/B amp. Especially the 60s, they are as fast & pissed off as they come.
That said, when I found out that the C+ RIs were pentode Simul it made a lot of sense why I liked them.

Wouldn't kick an OG off the block for me, but if I didn't already have an OG no way I'd pay today's prices & I'd be happy as a pig in shit with a RI.
Given all that, IMO the ONLY way I'd consider a JP over any MKII/III/IV would be for live use. The feature set of the V and JP are valuable for this, and live the generational nuance doesn't really matter.
Feature set aside, my favorite Marks live have consistently been the IIB+ and IV. They share a lot in common tonally, IMO, where the IIC+ and III have a different thing they share in the general EQ sit-ness.