I am not sure if you are looking to buy these guns or if you own them and are wondering what would work the best. Anyway use the one that fits you the best. Does the Mag-10 have a fixed choke?? If so this could limit your shot size with steel shot. I used to own a SP-10 it was a great shotgun. Sorry I can not tell you much about the Mag-10 but I am sure others on here can. A little more information would also help. What type of hunting(pass shooting, over decoys in a boat, lay out blind, pit blind, fence row ect... ect...).