I've been keeping fish for years, and I've only done freshwater. I have friends who have done saltwater, and say that it isn't all that much more difficult, but a whole lot more expensive. If someone asked me where to start, I'd say freshwater without a doubt. I think it'd just be awful if someone spent a bunch of time and money setting up a small reef tank, just to discover that the hobby isn't right for them, or worth it in their eyes. At least with freshwater, odds are that they wouldn't have "wasted" as much money.