Well with Paris-Tours it has traditionally been the length of the race which makes it harder, although this year's event was 250 km, which I suppose is just on the upper bound for Tour stages these days. Bear in mind as well that it is a classic as much through tradition as difficulty - it goes back to 1896. Saying that it is just the same as a Tour sprint stage is a very Tour-centric view of cycling - if you start to think like that then the Tour becomes the only thing on the calendar that matters. For me, the finish to Paris-Tours is usually much more tense than a Tour stage.
Well this year's parcours certainly wasn't made for sprinters, and the World Championships seldom (although sometimes) are. That's what I like about them; some years we get a climbers' course, some years we get a sprinters' course, but usually we get one in the kind of Ardennes classic mould. As for whether or not Ballan is the best in the world, you could say the same about pretty much anything. Are New Zealand the best rugby union team in the world? Most of the time, yes, but when it matters they do not produce. The Italians and Ballan were the best when it mattered. If you care about best over the course of the year or suchlike, well that's what the ProTour or the old World Rankings were meant to be about.