Yes the four blade Muzzey is smaller than the three blade muzzy.
In general the smaller the broadhead, the easier it gets to tune.
In general the slower the bow the easier it gets to tune.

For example it would be easier to tune a bow at 260 feet per second and a smaller broadhead. It is more diffucult to tune a 295 feet per second bow and a large broadhead.

That is one reason the smaller broadheads are getting popular is that people are figureing out that it is easier to tune on a faster rig..