Simply removing outlines from things doesn't really help, if something is designed with outlines in mind, it looks very strange without them, when they are simply removed.
When removing outlines, instead of just removing the line, you should really take advantage of the extra space provided. I did a quick, somewhat sloppy example of a 16x16 toughguy, with and without outlines:

I did the guy on the left first, copied him over and dropped the lines and repixeled on the right. Dropping the lines gave me much more room to define the character, it looked a bit cramped with them, but without it shows just fine. Its not really about outlines looking good or bad, when you get smaller, but more about getting the most value out of your pixels.
I like the RPG sprite size comparison, looks like it'd be good for a game in terms of showing different ages.