I just got the H&R Ultra Slug Hunter 12 this year. I really like it a lot. I agree with what someone else said: when shooting the high-velocity slugs out of this gun, it really packs a wallop. So far I've only shot Hornady SST 300 gr, and they seemed to do OK.

I plan on trying some different things next year as I got the gun pretty late in the season.

One reccomendation I would give: I'm 5' 10", 190# and after shooting 10 rounds of the Hornady SST with that gun, I wanted my mommy! It really packs a punch.

So if you're a smaller, or even average size guy, go with the 20 ga. It will be easier to manage, flatter shooting and have plenty of oomph to take a deer down.