I’ve got an 18” barrel with rifle gas and it’s certainly smoother than my 16” carbine gassed gun but the difference is not as drastic as it was back in the day. Buffers and springs help as well as properly sized gas ports. Back when I was shooting several Bushmaster carbines and a few other brands, they were terrible. Large ports and carbine buffers were really hard on parts.
Piston guns seem to have their own set of problems as well as not being as accurate as DI. But given a short barrel running suppressed in FA, HK seems to be the answer.
