Those are some good options, and each will serve very well as a general utilility EDC as well as a whittling knife. About the only opinion I'll register, is I'd rule out the copperhead. I really think you're going to want shorter blades for your whittling. I'm assuming you want to do more than cut points on sticks or strip bark off of twigs and branches. To do any kind of detailed carving you're going to want a smaller, shorter blade.
That said, the difference between the whittler or either of the 4" stockmans comes down to preference. In my opinion the blade configuration on the Whittler is better, as the clipped pen and spear pen blades are great for getting in tight. However, the stockman will fill out your hand better, and prevent hand fatigue. Plus, the larger sheepfoot blade is probably the best all around whitting blade among standard slipjoint blade shapes.
I think if I had to choose one I'd go with the 4" stockman. Regardless, I think you've made some good choices and whatever you go with will serve you well.
This has been a fun thread. Let us know what you choose!