I watched a couple of big Daltons with DA200's fly today. Very smooth planes with a good IMAC pilot and sounds good as well.
Yes, that 200, or any quad, will considerably bring down the vibrations on the airframe, and this in and of itself, cuts down on noise. the other great advantage is the smoothness of acceleration and the wide power band, therefore, you can actually have a "range" of power.
Any more details, I cannot mention, as I am not an engineer, but, somehow, must be related to two sets of cylinders firing at different times,, and each one is smaller (50 cc), lets say, than a 2 cylinder 170 (85 cc). the only downside is the plumbing and electrical wiring gets more complicated.