Turris did struggle when Spezza was injured a couple years back. But it was a great experience for him. Turris improved his game a lot since he came to Ottawa...errr..maybe the game was always there he just needed the change of scenery...either way...Turris was really good last year.
I am not so sure that he was the number one center last year....a lot say he was, but I didn't pay close enough attention to who was matched up against him each game. Did the other team view Turris as the most offensive threat? Did they play their best shut down lines against him? I would venture to say it was even between him and Spezza.
There wasn't a big difference between what Bergeron did and what Turris did. If you want the safe play its definately Bergeron.....and if there was a trade happening you should get Turris+ for Bergeron, no doubt.

IMO, Turris does have more to show though, and the gap may narrow even more next year.....