Which Callaway balls did you have in mind?
HX Tour (2006 version): good 3-piece ball for faster swing speeds. Very good distance (if you have the swing speed), excellent around the greens, and checks stick on the greens with some roll back.
HX Tour 56 (2006 version): another 3-piece ball that's softer than the HX Tour which makes it a little better for slower swing speeds. Same around the greens as the HX Tour.
Both Tour and Tour 56 covers are very thin, and will scuff easily with your wedges after a few holes. If you happen to hit the cement cart path, you're better off using a new ball at the next hole. At $40/dozen, it's not a ball worth losing.
Big Bertha (2006 and 2007 version): 2-piece ball that's good for slower swing speeds, beginners, and amateurs. Good distance. Not as much spin as the HX Tour/56 on the greens, but still very playable. Cover is more durable than the HX Tour/56. Didn't notice any difference between the '06 and '07 versions.
HX Pearl (2006 version): 3-piece ball. Very good for the slow/moderate swingers. Checks nice on the greens and sits when you need it. Cover has a pearlescent finish, which actually sparkles in the sun. Suppose to make it easier to find on the course. Similar finish to that of the Nike Mojo ball.
HX Hot '07 version: still haven't taken my sleeve out to the course yet to try this out.