Oh I'm all but certain he and Sabat are not even on speaking terms with Nadolny...more after this paragraph, but first let me say:
I respect your opinion too and am glad we can discuss this.
I also want to address using actors opinions on liking their performances more now in Kai or disliking an older VA... that does not matter to me. The reason is that kind of thinking first seeks to make an objective point based on subjective opinion which, no disrespect, is ironically illogical. For example, my favorite color is blue. If God were to tell me "You know I made that when I was just starting out creating stuff and I think in fact when I later made the color red I did a better job." I would respond "neat, God, but I still think you did better with blue." The creator's preference has no bearing on the audience's preference. A great example of this is the Star Wars franchise lol, but I digress.
Ok, now, truth be told
I can appreciate your point, after all "shouldn't the actor know what's best?"...he says realizing Sean Schemmel has said the "Hope of the Universe" Speech is still one of his favorites (see the Animazement discussion threads or Derek Padula's blog on the East v. West Pannel
and the Dragon Ball Z Blu ray Level sets which he and Sabat pushed hard on and Schemmel chose that for his Goku quote).
Now, true Mr. Schemmel did indeed make sure he said "Son Goku" in Kai and has been very involved in making the dub of Kai more accurate. All of those efforts aside, I find his passion lacking. Love his original work, love his passion, love he has opinions, but those really hold no water especially given their subjective nature.
Long story short, mad respect for you and your opinion, but we are both dug in and an actor's opinion cannot change that for me. And I am equally sure had Sabat said "I wish the old crew was back" that would only change your opinion of Sabat as a person and not Kai as a product. Fair?
SO, back on topic, well away from the of the "I don't" twitter quote: it seems to me that after reading and listening to several interviews that there may have been more than "creative differences" going on with the cast and that what was underlying a lot of this was fan service and break downs of friendships ie firing because people wouldn't play nice.
Rather than discuss it here, when I've got more concrete info I'll start a new topic. If after exhausting my last few follow ups I still don't have anything concrete I'll PM you what I got and you can decided for yourself. Cheers

"You might think you know everything there is to know about me, but really, you're not even CLOSE."
"Never give in--never, never, never, never, in nothing great or small, large or petty, never give in except to convictions of honour and good sense. Never yield to force; never yield to the apparently overwhelming might of the enemy." ~ Sir Winston Chruchill / Dragon Ball Z in a nutshell
How I enjoy the anime: