I guess it just depends on what you like accomplishing. If finishing guns 100% is your deal, then yeah, maybe don't prestige. I just feel like there's no possible way to even come close to finishing the majority of weapons though. If you don't prestige you'll miss out on the prestige challenges and lots of call-signs (you get lots of new ones every prestige just for hitting certain levels, like 35, 45, etc.).
I'd rather have a large majority of the call-signs and have the prestige challenges open to me then to have any of the guns completely finished. I'm not really concerned with the head-shot challenges either, seeing as you get camos from leveling your gun now instead of getting head-shots.
If it were me, I would prestige at least once so you can open up the prestige challenges. They have them for every weapon and then they also have an entire prestige category of challenges just like in MW2...