So far I've only cleared about half the Radio Towers/Outposts on the 1st Island, but as far as I can tell...
- the Bull (signature-shotgun) seems significantly more powerful than the other 2 shotguns I've used.
- the AMR (signature-sniper) is great... if you need to hit a single target with an artillery round! This thing is ridiculous. And keep in mind that every enemy (human and animal) will hear it when you pull the trigger.
- the suppressed Shredder (signature-SMG suppressed) is AWESOME! I really love this weapon! And I was really happy with my suppressed-MP9 before I unlocked the Shredder. I'd prefer the red-dot sight, but even with the semi-annoyingly bright blue sight, this Shredder is fantastic.
- I haven't really used the handguns much at all. But after reading some of the other comments here, I think I'll give the suppressed Shadow a try. (I haven't unlocked any of the other signature weapons yet.)
The only annoying thing with these "Signature-Weapons" is that apparently they've all been assembled by a weld-happy gunsmith. You cannot change ANYTHING on these. I'm surprised we can even change the magazine when we run out of ammo!
and @ darkfox:
Yeah, I'm on the fence... the Recurve-Bow is definitely an acquired taste. I think I'm going to like it a whole lot more once I finally unlock the "special" arrow options. Particularly the explosive tips.
I find it VERY difficult to range any distance farther than 30-40 meters. It also seems VERY inconsistent. For instance; Using a tree for target practice, I lined-up the 100-meter mark (marksman sight) and my 1st arrow appeared to land significantly short. But then my very next arrow landed significantly high (crouched, elevated position approximately 5 meters above the target). And I found this to be a consistent problem even after about 50+ tries.