When the Powerex 9000 charger reports "high" (internal resistance) they are at end of life.
It's been a while since I looked into it, but the "Pro" Powerex versions are (or at least used to be) intended for high-current applications - think photo flashes and such with high intermittent power draws. The "standard" version of the Powerex (which used to have "low self discharge" printed on the battery, later changed to "precharged") are rated something like a hundred mAh or so less than the Pro's in total capacity, yet actually have a lower self discharge rate and significantly higher recharge cycle count rating than the Pro's, meaning they are better suited to lower, but more-constant current applications, especially longer term as they age.
Since our gear tends to have a relatively constant current draw, and the most important metric for any battery that works for taping is reliability over time, the non-Pro versions seem to be better suited to our use. This was my conclusion four or so years back when I was replacing my batteries again and got relatively deep into it, deciding to remain with the regular versions rather than try the Pro's. The extra 100 total mAh was not worth the trade-off in decreased LSD and life-cycle performance to me, and I concluded the relatively small total capacity difference was likely to even out and possibly invert the trend after some regular use.
Anecdotal actual use:
I've used both regular Powex and regular Eneloop (which we use at work) for taping over the past decade and both seem to perform about the same in my experience.