I still think this is a lot about personal taste though. Because i think the TA-ZH1ES is an all in all improvement over the WM1Z while others like the WM1Z sound more.I don’t have the skills to perform a mod. I have previously heard what black gate caps can do so thought it could be fun to try something similar on the 1Z. To me it is an improvement as it just takes the 1Z sound and builds on it rather than altering it.
But i personally also like the M11 Plus LTD Sound a lot. Its a completely different sound as it is achromatic and so more ultra detailed, analytic and as close to perfection as possible with an insane SNR/THD/Channel separation that even beats the DMP-Z1. But a lot of people hate the sound from the THX AAA and think its very boring.
I can totally understand why some people prefer the WM1Z over the TA-ZH1ES as it is more colored but as i can enjoy chromatic amps as i can enjoy achromatic amps, for me the TA-ZH1ES is the ultimate device. Well beside the DMP-Z1 which sounds as good on a technical level but has this typical analog amp softness. Which again, i understand if people prefer it.
According to Sony, they tested all Brands of capacitors with the ZX2 that were on the market and decided that Panasonics OS-CON performed the best. When they developed the WM1 they tested again all brands and still found that OS-CON was the best, but weren't fully satisfied with them and so decided to build their own FTCAP based on the OS-CON.
So Sony decided against Black Gate Capacitors two times (or didn't test them which is unlikely as they are a japanese brand and they claimed they tested all they could get they hands on), but they decided due to personal taste for the OS-CON/FTCAP. It suited what they had in mind best. Maybe the detail they did not liked about the black gate capacitors is exactly the detail you like.
With chromatic amps, there is no right or wrong in the end.