Actually, what I think the word Pro means is a contraction of professional, i.e. you're using the computer as part of your work. In that case you probably want something that's very powerful right out of the box, and you're willing to pay for it (or at least get your boss to pay for it. Or write it off as a business expense). Also, Pro probably also means that you don't have a lot of time to spend diagnosing issues with bad memory sticks or fiddling around with hard drive upgrades.
