FME, I highly recommend double edged, fixed blade above anything for defensive use. Call me "old school" but hey, whatever floats your boat.
Also, I recommend something with a large/sturdy "tang/stop" (I'm drawing a blank on the proper terminology at the moment) at the base of the blade. Some "experts" may not agree with that, but the first time you strike a hard surface (such as a bone) with your blade you'll appreciate the feature (and so will your hands.)
Guard.
A deep finger choil will keep your hand from moving forward just like a good guard.