In short, yes he can defend. He reads the game well and is quick enough over 10 yards to get a foot in.
I think the difference is that Smyth has always been a box-to-box type CM who is better suited to CDM whereas Kane I always thought was more of a number 10 with that free role linking midfield and attack which he had so much success at Donny with. I also think Smyth is more aware of what's going on around him in terms of positional sense. While Kane can make that slide rule pass through the middle of the pitch or pick out a player with 4ft between 2 defenders, Smyth's ability when dropping deep means he has the time that he needs to take a touch or two before playing the best ball. Footballing intelligence, I guess? In some ways I think they'd complement each other really well as I think Kane in that deep role was one of the reasons we didn't make the play offs. All of this is opinion though from what I've seen in snippets of games throughout the season, and the quality is pretty damn poor, but as I said at the moment he has to be my most exciting prospect.
I'd be interested to hear what
@Nadi- has to say though as he may have a completely different outlook.