use the 20 for deer. i have a mossberg 500 20 ga and with the hornady sst 250 grain balistic tips it knocks the lungs out and i meen out. i have run them through 6 deer in the last 2 years including a 160 inch 9 point that weighed around 260 (at 15 feet running)and a 130 inch 10 point that weighed around 200 (at 90 - 100 yards running)and the 10 point went the farthest at fifty to seventy yards with a hole through the heart and both lungs and the ones who made it from where they were standing left blood trails that ray charles could follow. all of my friends are now beleivers while i cant get them to switch to 20 gauges they are all now shooting the hornadys. the 20 will kill deer and dont let them tell you otherwise i got the horns on the wall to prove it