How does the sound of the PCC88 and PCC189 compare to the 6922/6DJ8 and its iterations?

Check out the issue of Vacuum Tube Valley with the overview of the 6DJ8/6922. That would be much better than relying on the all-over-the-place anecdotal reports of different users! 

Vacuum Tube Valley issue 7: the top three choices: Amperex 7308PQ (very dimensional and musical, with smooth balanced highs) - Siemens 6DJ8 (60's West German) - balanced sound, smooth and detailed. This tube does almost everything right. 10M Mullard (60's British) - natural and sweet sound with good balance. Minimal, if any sibilance. For those on a budget, the JAN/Philips 6DJ8 and 6922 are capable of good sound at a reasonable price.

I recommend getting a copy of Vacuum Tube Valley issue 7. They test and report on a wide variety of these frame-grid tubes! And are trustworthy! BTW, I have at least two preamps that use these tubes - an ARC SP6 and a Conrad Johnson PV3. Hence my interest.