I'm sure you would agree that reliability is the most important factor when considering a personal defense firearm. While the Saiga-12 can be a very reliable and effective shotgun, it is inherently less reliable *as compared to the Mossberg 590* based on the nature of it's design. Specifically, I am referring to the fact that the shooter must understand the characteristics and operational philosophy behind the gas chamber selection valve (settings "1" and "2"). Not understanding this can result in malfunctions and/or damage to the gun. You can read all about that at forums.saiga-12.com. You could get the Saiga, pick some rounds, make sure they work and stick with them then don't make any changes. That would work (just make sure that while you're ensuring the gun functions reliably, it also isn't being damaged over time).