I recall expecting them to hire Jaleel White to do Sonic's voice in Adventure, and initially thinking Ryan Drummond's take was Jaleel White, just based on a few of his clips from demos and such.
But then, I think I prefer Drummond. In retrospect, White was really grating. I even prefer Jason Griffith to him, as wooden as he could be (although he got better before Colors, at least)... Kind of prefer Roger Craig Smith to all of them, though.
As far as polish goes, I always thought SA2 was the more polished. I can remember several fairly specific and easy-to-replicate bugs in SA1 - I can't really remember any in its sequel. Level design also usually felt a lot more focused, and in several instances, game mechanics (mapping light dash to a button, without having to charge up spin dash, was a pretty damned good idea, for instance, although keeping the action button overloaded when you had two other buttons that were by-and-large unused was not).