My friend and I decided to film some matches between the Spas 12 and the Model 1887 (after the model 1887 nerf). We did 2 games on rust with radar always on. We used the exact some class setup each time so that there would be no differences other than the guns we were using. Here are the setups we used
Bling (Akimbo, FMJ) Stopping Power Steady AIM
Bling (Red Dot, Grip) Stopping Power Steady Aim
In conclusion, Model 1887's with fmj + akimbo are superior to the Spas 12 with red dot and grip. However, if you're not using Bling, a Spas with Grip will always out-do 1887 Akimbo.