Call me a skeptic but I am always a little weary of a perfect unblimished record.Might sound odd but Facing the ultimate adversity via Defeat can tell you alot about there fortitude and character.Not to say that Undefeated's have not faced adversity,You can look into ANY undefeated record and find bumps in the road,be they draws,bad descisions,technical win's etc.
I really dont think you fully know about a fighter or "what" might have been until they are forced to deal with a lose or some serious threats.Did they fight through bad cuts,Climb off the mat from knockdown,gut out a war only to win by a point?Or were they just good to avoid it?You cant fault them for that either.
IMo,Records as a whole are overrated.Its a case by case process.Its not how many losses or wins you have,Its the how you arrived there.Adversity builds character.