I'd like to compare the crossbow to the military sniper.
100 DMG Headshot vs 99 (Raycast) + 1 (Projectile) DMG Headshot
Crossbow is all-projectile, military sniper is hitscan and projectile for that one last damage point.
Basically, both do 100 damage, but the Sniper's headshot hits instantly. The red shake and "pow" of the crit noise tends to surprise players and stop them on their tracks, letting the projectile hit.
Even worse, actual crossbow projectiles are slower than sniper trails it feels.
On a moving dude, if the crossbow misses, the military sniper will hit, and if the projectile misses, the player will do 99 dmg instead of 0.
5 shot kill Bodyshot vs 3 shot kill Bodyshot.
Military sniper wins due to its higher damage and raycast.
1 bolt per clip vs 4 bullets per clip; crossbow has to keep on reloading.
Military sniper wins.
Crossbow has to charge a very long time and slows you before loosing a bolt; Very, very bad.
Also, crossbow projectiles are so much skinnier than sniper shots, but this hardly affects them; the projectile model looks small but the actual size is actually huge!? So much tolerance for missing!
A few good points for crossbow.
Crossbow may win in one scenario in terms of head shots, where if you shoot a stationary alert player in the head, they're dead. If you military sniper one from far and are alarmed, moving away from the projectile, they'll take 99 damage.
However, this usually doesn't come into play very much.
Crossbow pushes players back a moderate amount.
Crossbow will always have 100% accuracy; although the projectiles are slow.
Crossbow bolts leave a fine trail unlike sniper's harsh glow, which may attract players if they want to be "stealthy".
However, the trail is still very visible.