Interesting thread. Unless restricted by law, I'd opt for a rifle over a shotgun. I've killed deer with muzzleloader, .270, and shotgun (though all my shotgunned deer were taken with buckshot while running dogs). I've acquired a rifled barrel for my 870 Express, and practiced with slugs... and they're like 3" buckshot when it comes to recoil. No fun. If your 30-06 or .270 feels like it kicks hard... shoot a box of slugs or buckshot ouit of a pump gun, and Mr. .270 will seem mild by comparison.

As does another poster... I opt for muzzleloader instead of a shotgun. I've a low-powered scope on mine, and I can place shots MUCH more precisely with it than I can with my iron-sighted shotgun, and can do so a lot further out. I know you can setup a shotgun to work well - fixed barrel, scope, good rifled shells - but that adds up to $$$ and a dedicated slug gun, and I've neither right now.

I, too, have concluded that where you hit the deer is much more important than what you hit him with.