I suspect that of the two choices, it will pretty much be pick what you like best. There are just too many good knives out there!!!
Seriously, both are made of good steel. I bet the CS is lighter, as the handle is kraton and there is no brass guard. The Boker has anice brass guard, if you want a more solid guard. You have to decide how solid of a guard you want in a backup knife.
I think you'd have to look around for a stainless CS dagger. I'm not sure if the peace keepers are made ion stainless anymore. On that same note, I bet the CS would be stronger, blade material wise, than the Boker.
Either one should make a fine backup dagger.