When you get sub-4" velocity loss in magnums becomes very big per inch, while recoil and muzzle blast increase proportionately. At some point you reach a point where the whole thing just stops making sense. Each has their preference, but for me it's 4" when we're talking magnum revolver cartridges.
As a defensive revolver, the sub 4" guns make a lot of sense when used with Specials because they handle so well.
