Piranjade: 3rd edition didn't have passive and active ball handling as far as a remember so most changes should concern skills and level-ups.
It should be enough if you look through the skill list and the categorization of skills. They have done away with "traits" for example. And "Very Long Legs" has changed.
There have been changes to some teams (I remember Ogres and Vampires) as well from 3rd edition to the current 6th edition.
Oh, there have been changes to fan factor as well, mainly making it less important.
Thanks for pointing out Very Long Legs, that's one skill that I would probably not have noticed had changed. Wood Elf catchers also has one less movie (but sprint instead), which I noticed when one of my players tripped over his own legs when I faced the AI
AFnord: No, I think that's a correct observation actually. His lack of block is a big problem. Hopefully he'll get some experience in the future though, because it looks like one of those players that can become a real beast .
rcthedigitalhero: The biggest downside to the Centaur is it can become SO good you rely on it too much, and as soon as it gets injured you lose your scoring edge. Your hobbies can be just as good, just less strength obviously :D
Sometimes it's nice to have a big battering ram though. That's at least how I view the centaur. They have too good bashy stats for me to view them as anything other than a basher. So that's probably how I'll develop it, give it block, tackle and such skills, and let my hobgobbos do the ball carrying.