For what it's worth,
I use the Hogue 12" L.O.P. on my 590a1 and the Knoxx recoil reducing stock on my 590. They both have their advantages depending on your needs.
The Hogue 12: L.O.P. - As others have stated it's hard to find a better stock to allow the shooter to square up behind the weapon. Having a comfortable control over the shotgun is a key factor in mitigating recoil. If you feel like you're having to reach for the pump, then you're already at a disadvantage. The shorter L.O.P. reduces the overall length which brings more of the weight closer in to your body making it easier to support its weight for longer periods of time. Adding a slip-on Limbsaver will add 1" to the overall length of the stock (13" on total mine) and make shooting full power 12ga loads feel like you're get'n tapped with a marshmallow. I use my 590a1 Hogue + Limbsaver set-up when I'm planning on putting a LOT of rounds through it. I broke the set-up in with 100 rounds of 2-3/4" slugs and went back the next day for some more. I couldn't believe how plush it was. The more traditional style grip does allow much easier manipulation of the action release and safety. For it's increased maneuverability, simplicity, and ease of operation, my 590a1 + Hogue set-up is my go to home defense shotgun.
Blackhawk Knoxx Recoil Reducing Stock - This stock does an AMAZING job of mitigating recoil and the adjustable L.O.P makes it highly adaptable to multiple shooters. My 590 started life as a PGO (pistol grip only) model and I upgraded to the Knoxx after getting used to the different style grip. The only downside with the Knoxx due to the pistol grip, is an awkward reach to the action release and the safety. My 590 + Knoxx is used almost exclusively for putting slugs on target at the shooting range. I mostly shoot it seated which severely limits my ability to get square behind the weapon, but the Knoxx system does an excellent job of absorbing recoil so my body doesn't have to. In this situation, the pistol grip allows for more comfortable control over the shotgun with my arm resting on the bench much like shooting a rifle.
Ok, so that was a lot more than I originally intended to post but I hope it helps.
I use the Hogue 12" L.O.P. on my 590a1 and the Knoxx recoil reducing stock on my 590. They both have their advantages depending on your needs.
The Hogue 12: L.O.P. - As others have stated it's hard to find a better stock to allow the shooter to square up behind the weapon. Having a comfortable control over the shotgun is a key factor in mitigating recoil. If you feel like you're having to reach for the pump, then you're already at a disadvantage. The shorter L.O.P. reduces the overall length which brings more of the weight closer in to your body making it easier to support its weight for longer periods of time. Adding a slip-on Limbsaver will add 1" to the overall length of the stock (13" on total mine) and make shooting full power 12ga loads feel like you're get'n tapped with a marshmallow. I use my 590a1 Hogue + Limbsaver set-up when I'm planning on putting a LOT of rounds through it. I broke the set-up in with 100 rounds of 2-3/4" slugs and went back the next day for some more. I couldn't believe how plush it was. The more traditional style grip does allow much easier manipulation of the action release and safety. For it's increased maneuverability, simplicity, and ease of operation, my 590a1 + Hogue set-up is my go to home defense shotgun.
Blackhawk Knoxx Recoil Reducing Stock - This stock does an AMAZING job of mitigating recoil and the adjustable L.O.P makes it highly adaptable to multiple shooters. My 590 started life as a PGO (pistol grip only) model and I upgraded to the Knoxx after getting used to the different style grip. The only downside with the Knoxx due to the pistol grip, is an awkward reach to the action release and the safety. My 590 + Knoxx is used almost exclusively for putting slugs on target at the shooting range. I mostly shoot it seated which severely limits my ability to get square behind the weapon, but the Knoxx system does an excellent job of absorbing recoil so my body doesn't have to. In this situation, the pistol grip allows for more comfortable control over the shotgun with my arm resting on the bench much like shooting a rifle.
Ok, so that was a lot more than I originally intended to post but I hope it helps.