Strength and regulating issues aside I've always felt the mono-block did not look as nice as chopper or dovetail lumps. There is the seam between the mono-block and the barrels, and things are bit broader in the beam.

I would think the mono-block being wider in the beam would make regulating a bit harder, but here the quality of the work probably makes a much bigger difference than choice of lumps.

In my own collection, including shotguns, I have all three types.