AVGN: An obnoxious, over-the-top nerd who can't act or deliver a line to save his life who relies solely on screaming things to make his point.
NC: A really good actor who's obnoxious and funny at the same time because he has these things called "timing", "vocal inflections", and a hilariously expressive face.
Don't want this topic to delve into the classic Nerd/NC debate, but really now. Most of the best AVGN videos are the ones where he tones down the ranting, or at least condenses them into bite-sized sections, so it's hardly fair to say he "relies solely on screaming" to be funny. The NC, on the other hand, can't go two sentences without shrieking, wailing, and/or flailing his hands and arms around like he's got... problems. And the Nerd's faces are about 1000x better and more expressive, not to mention varied.
Carry on!
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http://www.youtube.com/watch?v=SBpfwpOPXNc&NR=1&feature=fvwp
I watch Planet Chasers Starlight Excellent all day, every day.