The Andrew Hou image, while superior, would look odd on the bookshelf next to the other 4e books.
Eh, I don't think your ultimate evil image really jives with chaotic evil or the themes of most demons. I think incongruous bestial animal features go well with a primal degenerate destructive malevolent force. Demogorgon fits well in a concept of Chaotic Evil for me.
A devil is classically closer to your image of evil smooth talkers but they still have bat and goat animal features, neither of which really summons up intelligence or smooth talking outside of the traditional image of devils as such.
The concept of Demogorgan is very, very cool.
A being with two heads each vying to be the soul possessor of one body, constantly subtly warring against each other with the brooding premise that should one of the two heads win, Demogorgan would be unstoppable force of destruction all the while projecting an air that the two personalities are in fact one, is awesome.
Then they gave this great idea two baboon heads and tentacled arms.
Sigh.
So much promise.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.