Myself, I tend to prefer the subs. I usually find that in dubs, the VAs don't really do a very good job of it (the exception being Cowboy Bebop, the quality of which is remarkable). I much prefer the acting quality of the Japanese voice actors over the English ones most all of the time.
That being said, here is my opinion on the Trigun dub.
Spoilers ahead.
The VA for Vash, I think he does a pretty good job of it. He hams it up at the right moments, and seems to do an ok job on the more dramatic scenes. I have no problem with Meryl's either, overall. I think the actress chosen for Meryl was a good call. However, I have one reason why I do not like to watch the Trigun dub unless I have to, aside from my general preference for subs. One reason that completely turned me off to the Trigun dub.
That reason is the English VA of "Stungun" Millie Thompson.
Firstly, Millie's VA in general is just annoying to me with almost every word. Also, there is one scene in particular that instantly made me despise Millie's VA.
My first time through, I watched the sub (of course). After Millie hears that Wolfwood died, her sobs of anguish cut straight through me. She sounded like someone had ripped a hole in her chest, tore out her heart, and put it through a shredder while she watched. She actually sounded like a part of her had died along with Wolfwood. Like her entire world had completely fallen apart and that her heart had been shattered into a thousand pieces.
Then, I made the MISTAKE of seeing what the English version sounded like.
The woman was AWFUL!! I swear to God, you have never heard a more unrealistic, unconvincing, flat-out SHITTY portrayal of suffering and ultimate heartache in your LIFE!! She sounded like a child that was faking a temper tantrum to get a shiny new toy. Like the entire time she was trying to sound like her entire world had just collapsed on her, she was thinking about some funny joke as colleague had mentioned earlier! I couldn't BELIEVE how awful she was during one of the most powerful scenes in the series!!
Japanese Millie made me wish there was something, anything I could do to help her, to make her feel better, to ease her suffering. Japanese Millie cut through my every defense and affected me deeply. English Millie made me want to hunt down whoever the VA was and ask her how she could POSSIBLY be that terrible!!
</end rant>
That's my two cents, anyway.
