Michael Caloz is my favorite too, probably because he was the first.
Oliver Grainger is passable, though at times, especially whenever D.W. would hit emphasis, he sounded like he was losing his voice.
Jason Szwimmer, likewise, did a passable job with D.W., a little better than Oliver, but still not up to Michael's level. I will say that at times, Jason's D.W. could sound a little nasally, almost as if she had a cold, but then again, that worked well whenever D.W. would start whining about something.
Can't really give much of an opinion on the others since I haven't watched a whole lot of Seasons 9-15, though I will say that during that time, D.W. pretty suffered the same problem that Arthur did, in that her voice was far too high for her character.