As has been stated, length of pull, drop at nose and heel, cast off/on, pitch, ect. all affect how a gun fits a particular shooter and how well that shooter can shoot that gun. Michael Yardley, in his book Gunfitting, says "fit is important--vitally important." To answer the op's question about length of pull, Yardley says "90% of men are accommodated in the range of 14-15 1/2"." He also states that "a gun with a long stock points better than a gun with a short stock and, providing it is not too long, controls recoil better".
Those that can afford a bespoke gun will spend hours on the trap/sheet field with a try-stocked gun arriving at the perfect stock fit. Since a shotgun is pointed and not aimed as is a rifle and the eye is the rear sight, the gun must come up the same way consistently and repeatedly without any adjusting for sight picture. With a rifle the shooter has time to adjust to stock vagarities but not with a shotgun--it must fit.