As for the Swarm, I almost drank the Kool Aid when I was new to the 20g arena..
The SSX on the other hand has been very good for me in the 20s.. In my long barreled 870 it out performed my Pure Gold Tempests 555 and 570 and also Pure Gold Ported along with a few other chokes with a variety of ammo, Nitro 7s, FEd HW 7s and Hevi 7s.. All three ammos through it produced very good numbers and patterns.
I also Opted for the SSX in two short barreled Remingtons one a 1187 and one a 870 after testing it against PG Temp 555 and 570, RSF, Undertaker with the Fed HW 7s.. Consistently 145 to 155 in both guns..