To me they drop fastest to slowest: tomahawk fastest ballistic knife normal bow slowest
That is of course based on impressions and not numbers/variables. If its true, though, then the drop won't be comparatively relevant because it would just make the tomahawk that much "worst" and the bow that much "better." Unless maybe you're considering a kill from an elevated position or something..
The Crossbow has 4180 Speed and 90 Up (not relative). It is exceptionally fast but also will rise up a bit with a level shot before dropping.
The Ballistic Knife has a 2180 Speed and 90 Up.
Using /centerview to give me a perfect 90° facing parallel to the ground and one of the many long flat surfaces that make up most of the Black Ops maps, the two projectiles travel an expected 20~ and 40~ meter distance before hitting the ground.