I like them both. The 25-06 is a better dual purpose big game/varmint caliber. The 7mm-08 is a better dual purpose deer and other medium-big game round. It's a simple bullet selection/trajectory option. Really, both kick about the same, to me. To 300 yards, the 25 is on a string. The 7mm-08, not so much...though it will do it. Your choice. Personally, I don't see the sense in short-action cartridges in a single shot rifle...but that's me. I'd think a .280 remington would make sense over the 7mm-08, at least in a TC...unless there are recoil, barrel length, etc. concerns?
Here's a thought: Let the ducks work and decoy.