@NER:
Dude come on, wasn't it stated(or at least heavily implied) that if you master your fruit enough or/and have haki stronger than your opponet you'll be able to bypass their defense? :| obviously Law did one of these two things, or both of them, and thats how he managed to cut vergo.
The only conclusion you can draw from the Law vs Vergo fight, is that perhaps Law's haki was strong enough that his attack could overcome Vergo's defensive haki.
That doesn't mean Law's haki > Vergo's haki. It simply would mean Law's offensive haki + his ability > Vergo's defensive haki.
Offensive force and defensive force are not a simple mathematical equal.