I take it you don't own a suppressor.Also is that suppose to be a crossbow? Looks like a regular bow to me. Anyways, not much else out there that is going to be deadly silent than a bow. Still too much mechanical noise from guns, even with a decent suppressor. Not to mention muzzle flash.
I do, and you're wrong. Gun won't cycle with my subsonic rounds so its a bit annoying, but its virtually silent and far more compact and with a greater range and higher accuracy than a crossbow, not to mention that you don't see where a shot comes from with a bullet.
The only logical reason to use a crossbow from a combat perspective is if you want to quietly launch specialized projectiles (tracking beacon, explosive charge, etc).