I think part of the answer, other than personal preferences, has to do with the gauge, ammunition used and ultimate end purpose of the shotgun in question. If you prefer a side-by-side for heavy loads, long range work and with long barrels and tight chokes, I would probably go for the boxlock. When John and Spencer Olin developed the 3" Magnum load- with the Askins-Sweeny barrels and chokes of the 1920's- they went with AH Fox, who then developed the heavy and solid HE Magnum for that load. Ditto a few years later, when they took the already potent 2 & 7/8" 10 gauge and bumped it up to 3 & 1/2"- they went to Lou Smith at Ithaca and his designers re-vamped slightly the fine NID boxlock for that cannon. But for a fine upland 12 bore, I'd take the English styled sidelock made by R.G. Owen for the late Captain Paul A. Curtis- shown in his book "Guns and Gunning"- 1934. There is something about a fine sidelock with a straight handed grip and a splinter forearm that almost defines class-- and if you chose not to agree with me there, that is fine-- but consider this- how many existing boxlocks, Parkers and M21's, were treated to faux sidelocks by Pachmyer and others in past years??
