I had the PD MPS5 for a few months and sold it because the mids and lower mids seemed to lack control on redbook only, where they sounded a little woozy. I did like the tonal signature though, no glare or "digital" glassy upper mids in redbook. I hear the new software or long break in adds more control now (others I spoke to heard exactly what I did), but I have not heard it since I sold it. (SACD had none of the redbook problems and was superb, period.)
New X-upgrade is warmer on redbook with less glare and more depth and very nicely slightly recessed midrange, which I enjoy, and lots of micro imaging detail and rounded sounds with real-sounding boundaries. SACD is a joy with almost all recordings, making me wish everything was SACD. No need to analyze SACD sound on the X'd CDSA, but no digital pain and all is well, no need for analog with SACD, which beats vinyl for me. It's just from memory, but I think there is a smidge more unforced detail and relaxation on the X with SACD, but as I said, the MPS5 is superb on SACD too, and I could be happy with either for HiRez.