By rating each of their tires in a dozen different categories, Schwalbe makes it easy to do this kind of comparison their web site (assuming you trust Schwalbe's evaluation of their own tires, and I don't know why you wouldn't, or at least I don't know why you would trust anybody else's evaluation more).
Since you didn't even list rolling resistance as a priority, the weight difference is immaterial. You also didn't mention ride quality. Many people say that riding heavy, stiff tires is like riding on wood wheels and sucks all the joy out of riding. Who cares if you can go a million miles on one set of tires without a flat if there is no joy in it. How much are you willing to sacrifice to get a flat every two years vs. a flat every one year? Flats are certainly annoying, but not that hard to fix.
It's also important to note that the Mondial comes in both a folding version and a wire bead version, and they are completely different tires. Almost everything about these two tires is different except the color and the tread pattern, which makes it very odd that Schwalbe only gives one set of ratings. Since there's a 2-to-1 difference in price, would you really expect them to perform the same? I don't think so.
For protection, the Plus Tour gets a 6 and the Mondial gets a 5. Score one for the Plus Tour. For off road, the Plus Tour gets a 3 and the Mondial gets a 4. Score one for the Mondial. For durability, they both get a 6. I would think, however, that the Plus Tour would last darn near forever since the rubber is about 6 inches thick
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It's almost a tie between these two. You might want to look at some of the other criteria that Schwalbe rates.
