Kovalchuk. Spezza has superior vision and playmaking skills, and might have a better work ethic, but Kovalchuk is better in every other way. Both will be very, very good players, but Kovalchuk could be the best in the league.
I think they have the same work ethic, none don't really impress me in that area.
I picked Kovalchuk because he's a year and a half ahead of Spezza and has similar if not better upside. Not Spezza's fault but it's enough for me to go that route.
Actually, Spezza's work ethic is vastly, vastly under-rated. He worked unbelievably hard all summer training with Gary Roberts, famous for his off-season training. He has worked on his all-round game, and has improved all of his flaws. He's possibly our fastest center now, although Fisher is close. Overall, the common misconception that Spezza is still that immature kid who didn't back-check, had a training regime comparable to Mario Lemieux in the 80's, and still floats and doesn't skater well or much at all, is still present in many people's minds.
Kovalchuk has the edge right now. He's making himself impossible to ignore with his second hatrick of the season, and he gave me no choice but to vote for him.
I wouldn't count out Spezza just yet, though. He's definitely behind Kovalchuk right now, but he's going to start catching up soon. His play sometimes can be absolutely remarkable, and I'm hoping that he'll one day surpass his draft-mate, but the edge definitely goes to Ilya.