I think the VA discussion is mostly a product of two issues: Comic book dialogue does not necessarily make good animation dialogue; a very good voice actor can overcome this.
While there's certainly plenty of dialogue in TAS that warrants the "comic book dialogue" descriptor (including the famous "I am vengeance" line), the writers were most certainly writing for animation. Dini's actually discussed how different it was writing for Detective than it was writing for TAS, and it's not just because he could use Hush and Mr. Zsasz.
Mark Hamill and the character of the Joker in particular happen to be good examples of this. Joker is both a hard character to write and deliver, and has had so many different incarnations and personalities that no one can really agree what sort of crazy he's supposed to be.
Indeed, and lampshaded directly in Spiner's multiple-personality line.
I'll grant that so far this Joker isn't particularly jokey, but neither was Jerry Robinson's original back in Batman #1. I'm hoping we see some more development of him, but I don't mind this take so far. And I like that they're using a particularly un-Hamilly Joker given that their Batman is pretty much just doing his best Conroy impression.
Conroy also has a great Bruce Wayne.
Indeed, and it was a pity (though understandable) that JL used him so little. I loved TAS's version of Bruce as a guy who'll go volunteer in a soup kitchen.
In that sense you can look at the DCAU as a slow erosion of Bruce Wayne until only Batman remains. He's more dour and violent in The New Batman Adventures, but still helps people in his Bruce Wayne guise, as seen in "
Things Change Old Wounds", where Nightwing recounts how he quit after Batman got too rough with a thug, only to find out that Bruce went on to offer the same thug a job. Then, in Justice League, the only time we really see him as Bruce is when he dances with Diana; he appears out of costume on a couple other occasions -- when he unmasks to his teammates and when he does a costume change in the Old West -- but he's still very much Batman in those cases. And by the Batman Beyond future, the upbeat, good-natured Bruce Wayne is gone entirely, replaced with a lonely, bitter old hermit.
That was initially my big gripe with Batman Beyond -- I quite simply didn't want Bruce to end up that way. I wanted him to conquer his darkness and for the philanthropist in the soup kitchen to win out over the tortured avenger crying out for Mommy and Daddy.
Of course, Old Bruce is in fact fucking awesome and I wouldn't have had Batman Beyond any other way (though Morrison's alt version with Damian, not Bruce, as Terry's mentor is damned tantalizing), but I still like a Bruce Wayne who isn't quite so obsessed and can still enjoy life and make the world a better place by going out in a business suit in the daytime.
Which brings us back to one of my favorite scenes in YJ: Bruce dropping what he's doing to shoot hoops with Dick.
YJ doesn't give us much of the characters in their civilian identities, which tends to happen in team shows -- Bruce wasn't pushed out of JL just because the series was continuing Batman's existing character arc; we didn't see more than five minutes of any of the other heroes' civilian identities either. And Teen Titans was all-costumes, all the time, with the characters' real names never even spoken. So little character moments like that stand out all the more -- and that's one of the defining moments for this Batman. And, for that matter, this Superman -- you'd typically assume Batman to be the detached, uncaring father figure and Superman to be the nurturer, but this show takes it in the reverse direction. And it makes sense! For a character whose defining moment is the loss of his parents, and who explicitly adopted an orphan boy out of empathy for his tragedy? Of course he's going to be warmer than the farm-raised alien who's just found out that a shady government agency stole his DNA and used it to create a dickish, angst-ridden teenager.
Essentially, Batman Beyond explicitly stated that Batman is who he really is and Bruce is the mask, and Nolan ran with that notion as well. And it's an interesting way to look at the character! But not the only one, as indeed Dini himself wrote in that bit of Bat-Mite dialogue I referenced a few paragraphs up.