I think the issue of effectiveness has less to do with what techniques you know and a lot more to do with how you handle yourself when under serious pressure and how well you stick to the principles you've been training in all along (regardless of what system you do).
Anyone can put a few rounds into a paper target accurately or execute a certain strike or technique very well when not under extreme pressure. Do the same thing with someone rushing at you with full intent to seriously damage you and/or with a weapon to take you out and the accuracy and the effectiveness of something learnt under calm conditions may not be so guaranteed. Ron's point "C" above is very apt imo.
It makes no sense imo to learn an entire bag of methods to defend oneself with and have that bag removed from your grasp because your adrenaline dump caused you to freeze or lose motor control. To me the techniques are very secondary.
Part of why Judo, MMA and BJJ type systems work in reality to an extent have to do with the practitioner getting accustomed to applying techniques under pressure and adrenal stress. Aikido training done with similar methods regarding operating under pressure and this sort of stress can have similar results.
Just a few thoughts.