I, too, think it's highly unlikely that moderate changes in blade shape on a folding knife would have any real impact on the outcome of a defensive situation -- though I'm thrilled to pieces to argue about blade shape.
I tend to use thrusts and hooking, both of which favor straighter blades. For me, basically, straighter is better. A sharp point is also advantageous -- which means, BTW, that the Americanized tanto as usually made is not a good choice. Though again, hard to believe that would make a critical difference.
For slashing, the standard view is that curved blades are better. But Mike Janich claims that, for the kind of strikes you see in a knife defense situation, with a small blade, a straight edge actually penetrates better for slashing. Hence the Spyderco Ronin, with its straight edge. I find that for long controlled slashing/cutting (i.e., not the type typical of a defensive situation) curved works better, but for defensive use where you'll have minimal time of contact, and the slice is very uncontrolled, and contact may occur at a non-optimal part of the stroke, a straight edge may very well be the better choice for the slasher.
Joe