I agree with tree climber and outdoorsman, I' m assuming oldup got burned by a .410 once, or hasn' t used one much, or hasn' t used one in 3" much (or is a poor shot[:-]). As long as you do your part, i.e. don' t miss, a 3" chamber .410 will rip a squirrel out of the trees, just don' t use the same light shot as you would for larger bores, I use 6 shot, occasionally I use winchesters 5#' s, but since they cost an arm and a leg to blow on squirrels, they usually get reserved for coyotes. Neither the 20ga or the .410 really excell this time of year, since the leaves and new green branches are in full swing, and trees are pretty dense, but the 20ga won' t give a noticeable increase in performance, leaves block lots of shot just as easily as a little. I' ve used .410 in 3" chambers for all my life, and have yet to have a squirrel argue about getting hit, I don' t know how many free Mepps lures I' ve gotten over the years, but at one point I had a full ' bassin box' of free Mepps lures (check out their website, they buy squirrel tails, either for cash or for credit towards lures), like I said, it takes about 10-15tails per lure, and I usually get two or three lures a year, due ONLY to hunting with a .410, so I guess the proof is in the pudding.