I own both. It's an individual thing. I feel the K-80 kicks more, but it is lighter. Many people that shoot K-80's claim they are soft shooting. The trigger on the Seitz can be adjusted for weight by the owner, and I feel less complicated. Depends how they feel to YOU.
Machine, I own and shoot both along with p-guns, no axe to grind, shoot both, adjust the k-80 to your liking and have at it, then shoot a Seitz remember to shoot one that shoots higher, at least 6 inches higher to make up for the faster trigger, unfortunately many shooters who have tried to shoot Seitz and Bowens were not made aware of this and subsequently had trouble shooting them when shooting back to back with their K guns and P guns, shoot both, just make sure when you buy your Seitz to have it impact the same as the Seitz you shot successfully. enjoy your journey! incinerate em!
Like mentioned above, it really depends on your shooting style. They are two very different guns. I just sold my seitz and could never get used to it. It was a very, very nice gun that would last many lifetimes but it wasn't the gun for me. I just bought a K-80 and have been shooting it for two weeks and have shot a 98 and added a 100 straight last night. I could not even come close to that with the Seitz. It was by no means the Seitz fault, it just wasn't right for me.
PerazziBigBore, I will have to disagree with you on the balance of the seitz. As we all know, the Silver Seitz is a copy of the original Tom Seitz design. Tom Seitz designed the gun to be stock heavy to increase barrel speed. The K-80 is much more evenly balanced than a Seitz. The K-80 is lighter but the Silver Seitz swings to the bird much, much faster than a K-80. There's no comparison their. My problem, along with many others is that the Seitz is just too quick to the bird and you blow right by it. Some people can shoot them and some people can't.
My opinion would be to by the K-80. It is a more versatile gun that you can set up to shoot many different games with different barrels and stocks. It will last much longer than you need it to and with proper care will give you a lifetime of shooting.