Woohoo...finally got my tactical shotgun today...stumbled across a fair deal actually (which hardly ever has been known to happen to me..:-)  Anyway, it's a Remington Express mag 870, with snap sling, 6 round sidesaddle, 2 round extension, just a bead but for 275 I didn't think it was a bad deal.  Looks like maybe 50 rounds through it, sling looks brand new.  Well...anyway I shot a friends 590 with a pistol grip choate stock, 20 inch barrel this weekend and with the same ammo, this gun seems to recoil much more than the Mossy.  Now, i've been shooting shotguns for a long time and never had a problem with recoil, but this one gave me a good cheek slap, not bad on the shoulder.  I'm wondering, are the 590's backbored like the 835, is it the longer barrel, the choate stock, or just in my head?  Any comparitive experience out there?

some addtions you might want to consider:

Choate pistol grip (www.uws.com)
Surefire forearm
and my favorite addtion...Trijicon ghost ring sights

Mine is set up this way (with all the goodies you mentioned as well) and it shoots as acurate as a rifle.  Yes it kicks but don't all shotguns?  If low recoil is what you want then go with the AR.  If a whole lot of whoop ass is what you NEED, then go with 12ga slug.  

My .02