Zetterberg is the player they use to shut down opponents(Ie. Crosby, Perry etc.)
Zetterberg is just as effective of defensive player than anyone in the league, he just isn't a true center, so like many wingers he doesn't nearly get the credit he deserves.
Datsyuk is flashier, Z will never make the kinda plays Datsyuk does however when Babcock needs somebody to shut a guy down he goes with Z. This is a great problem to have so this isn't a Dats vs Z thing.
I love to watch Z in the zone, his stick work and positioning is so good, Datsyuk's stick work is obviously even better but that s*** ain't even human.