I have the Shreditor 112's (189cm) and I have like 5 days on Jeffreys.
Love both skis, but they are different. However if you told me I had to ski one ski for the rest of my life in every condition, I'd probably pick one of those two.
The K2's go on sale a lot, they are easy to get deals on. They are a little softer, but not terribly so, they're also pretty rockered and tapered. They ski reasonably short, but the 189cm is a big ski, so, for me at least, they did a good job balancing quickness and the ability to swivel, while also being able to open it up.
The ON3P's are sick. They'll offer more support and stability, they are stiffer, more cambered, less tapered and lighter. I'd say they are more versatile, and more substantial, while still being able to play, I'd put them more on the chargy end of the spectrum that the K2, but I still found them to be incredibly fun, and are way better when you are hauling in variable conditions.
It's worth noting that neither of these skis are coming back next year. The Kartel 108 / 116 and Marksman take their places.
I'm really hoping the Kartel 108 takes that ultimate do-it-all spot, but we shall see!