The bottom row's AA is slightly darker than the upper r- Dang it Dusty beat me to it.
About the highlights being too distracting, on my monitor it looks great so I'd go for the third or first row. But thats just me.
As far as critique go's, everything looks very well done, the expressions are wonderful. They're so full of life.
One thing that sticks out to me is the sad emotion just looks like he smells something rancid, but he's not actually sad. One way you could fix that
would be to move the middle section of the mouth one pixel up, and have his eyes downcast.
And maybe on the laughing one you should raise the outer eyebrows a pixel or two, 'cause right now he looks a little nervous.
But as I said before these emoticons look very nice. Happy pixeling!