I've watched about half of the video so far, and the reason the hand-held meter is "so much better" (at least the way this guy is using it), is because he's only comparing it to the evaluative metering on a 5D (not mkII, at least according to the info made available during the video). Of course the hand-held meter is better in these situations!
This would have been a much more valuable comparison had he been putting his light meter up against the spot meter of a more advanced, modern camera system. Of course, this video is direct from Sekonic, so they want to make the camera metering look as bad as they can so we'll all run out and buy meters.
I'm not saying there's anything wrong with a hand-held meter, and yes they usually are better, but this video is not a great example of why... It's actually pretty disingenuous.
And it's a terrible video, from a technical standpoint. That shaky camera work combined with the reversed fields is enough to give me motion sickness. 
/crabby guy who wants things done right 
Well..there are plenty of other videos showing the reason that incident meters are much better at ensuring a good exposure in many many situations...take your pick.
His "root point" would be that a reflective meter is just not up to snuff as an incident meter is...no matter what camera it's in....I have another video where a MKII IS use and the result is the same...it's only good on "average" scenes where there's "average distribution of tones"
And even then it's not "spot on.....

I've been more and more convinced of it's usefulness as I've used it in a variety of situations over the last week or two.
I've used it at the gym where my step-son wrestles and it was spot on when my camera meter was not.
Also, I took it to work to show a guy and here was the test:
We pointed the camera at a guy and centered the meter...then we moved the camera a bit and changed the meter by a full stop....not even 5 feet from the first spot....how who are we supposed to know which exposure is correct and how much the camera was getting fooled at any given moment except to do a wild guess?
Then we pulled out the incidence meter and hit the button...instant exposure settings as long as the lighting in the building didn't change...super easy...super confidence.
In my mind...I'd never go back to chimping and hoping.