For me, I'd have to say Veronica Taylor is my pick. Sarah Natochenny works for an older, more mature Ash, but is far too rough and deep for my taste. She doesn't fit the fact that he is 10 years old. No boy has a voice that deep at that age. I'm just being realistic and using common sense...Taylor was more fitting for the character to me in general.
I've noticed Sarah's improved in Black and White, but something about her voice is still artificial/fake. You can hear her straining to do the voice, and it sounds very forced and dry at times. Her laugh is still just awful. It sounds like Fran the Nanny...no joke.
Taylor was high pitched at first, yes, but Ash is a 10 year old boy. It complements him perfectly in that respect. Taylor also proved she could do deeper Ash more smoothly and less roughly/strained than Sarah in Advanced Generation, so I would still prefer that voice for mature Ash.
Though, in general, I prefer every single dub voice in the 4Kids dub to the current dub ones. The current ones are decent, and I will say that much, but nothing really amazing or passionate in their performances at all. Some of the voices they use are extremely inappropriate given the ages of many of the characters.
I will say Sarah's Ash sounds more like a boy than it ever has before, and it's a decent performance now, but Veronica's Ash was better, IMO.
I have to agree Michele's May bothers me more than Sarah's Ash, though. I still prefer Veronica for both chars voices, though.