I would have to disagree with robacker, I believe that the Styleside is worth a little more, but not by much.

Dont buy a classic anything if you think you will make $$ on it. But, if both were in identical condition located in the same area of US. the step side is worth a little 10% more cause less were made. I posted a pic of my 65 f100 project. its complete but to be worth serious money a new paint job is needed.

Sources: Factory production figs from Ford.