S-F daggers are cool, but are too weak for utility use. A-F daggers on the other hand are so thick that they really aren't any good at slicing anything, only stabbing. However, the single edged A-F dagger is a great work knife. For strictly SD use, the only advantages the Applegate version offer are an improved crossguard to prevent snapping your thumbnail while doing a thrust, and the handle is shaped so you know where the blade is.
The bottom line is any version of the S-F knife is a great SD knife, because it will kill an attacker, and if it breaks in the proccess, who cares?.