I vote 2.5x 20mm Leupold....... Because I've got two; I've had the same one on a 12 ga. 870 slug gun since 1989 and have no desire for anything else, there's enough magnification for anything in slug range but it also has a wide field of view up close. The other one's been on a Mossberg 500A 12 ga. Turkey gun since 2001, that one's got the "turkey ranger" reticle but I don't think they make that reticle anymore (?). They're both tough as nails, been through nasty weather and some hard knocks, (the 870 once fell out of a tree, luckily it was empty, and the scope never lost zero) and neither one has ever had a problem. The 1-4x 20mm Leupold would also be O.K. ( I have one of those on a 30-30 Marlin) . But the 2.5x is probably a bit lighter and a little more compact. If you could look through one you'd see what I mean by enough magnification for a slug gun yet a great field of view at closer range. On a slug gun I always say "fixed power" because I've had too many times where there's no time to play around with changing the magnification on the scope and a fixed 2.5x has you covered from spitting distance to maximum slug gun range.