Playing Breacher, there is no real choice of shotguns. Both perform exactly the same with the only difference being the iron sights.
I know that pump shotguns are very similar with each other down to the basics, but I have a couple ideas on how to individualize the two shotguns.
Since the M870 has a solid stock, ADS when shooting should be more stable with follow-up shooting.
Since the TOZ194 has no stock, the weapon should be lighter in weight and faster ADS transition, but follow-up shooting is slightly unstable and recoil is higher.