(Carl Sagan in the background intoning:
"There are billions and billions of yokomenuchi variations, each one unique and special.")
Well I think it's positive to learn how to deal with different attacks, since the bad guy in the street is not going to perform a perfect yokomenuchi. It has never been a difficult technique for me. I would have voted Ushiro ryokata dori (both shoulders grab from the back), because that's definitely the most "difficult to handle" attack for me, since most of my training partners are shorter than me so it's hard for me to get out of the grab without messing up my hair. And if something drives me crazy is to mess up my hair. No, really, it does.