Yes, M3 design is closer to a long-stroke piston design, even though it uses inertia (or manual) to cycle. The bolt carrier group has the bolt and a big long "carrier" to accommodate the big spring in the front. It's much more weight to move in cycling. It causes more wobbles.
Beretta 1301 is a long-stroke piston design. Examples are AK-47, Sig 556, PWS MK-series, etc. Benelli M4 is a short-stroke piston design. Examples are SIG MCX, SCAR, LWRC, etc. Long-stroke and short-stroke have different design philosophy and tradeoffs. But, in general, long-stroke piston designs have larger and heavier bolt carrier groups, which tend to cause more wobbles and reduce accuracy. I was so curious why Beretta 1301 long-stroke design could be "better" than M4's simple design as people claimed. Well, it's not. I went through the whole nine yards to confirm my thought. But, anyhow, I don't regret getting 1301 at all. It's still a great shotgun. Just not "military" level.
Back to M3 vs M4. I read the recent article in American Rifleman saying that USMC should adopt M3 instead of M4. Well, I am not sure if the author really got the fundamental differences of the two designs. Using inertia to cycle a heavier bolt carrier group wouldn't be the most robust solution for combat. M3 is a great tradeoff if one switches between lethal and non-lethal rounds, and is a perfect shotgun for civilizes. For marines who don't care for non-lethal rounds, M4 is more appropriate.
P.S. I am not against long-stroke piston designs. I got Sig 556 and PWS.