In a 4v1 cluster the Gnasher will always beat the Sawed Off. For individuals, sure.
The Sawed off is a terrible gun because its existence, as mentioned before, is unnecessary. There is no need to have a different shotgun because in Gears 3 the rifles have been made more than capable.
The SOS is also a weapon that just isn't fun. I've used it by mistake a couple times (Loadout randomly getting changed...idk why). The fact that I have to get the fuck out after getting off/missing a shot is just not engaging. Shotgun battles are one of the most intense things about gears. With the SOS there are no shotgun battles. People rush in, press RT in general direction, and then run away. How is that fun? When I rush, I want to start going off on multiple people. That, or tango with a motherfucker and the better man will come out on top. The SOS defines the tactics of a pussy. I don't really get mad at anything but it almost irritates me to see people rush in/camp behind corners with a sawed off, jump out, press RT, then RUN away even if the person isn't pursuing them. Meh.
One on One, mure. But when there are multiple people involved (and this happens a lot), the SOS is annoying. And when 4-5 people on a team are using it? Smh...