So, as I understand it, it breaks down like this:
Butler has more power, a lower average, no speed, and is destined to be a DH because he's limited defensively. He's also closer to contributing because he's spent a year in the minors.
Think: David Ortiz
Gordon is the purer hitter, with less power, more speed, and will stick at 3b. He's at least a year away, but is can't miss.
Think: Todd Helton but at 3b.
That about it?