Is it worth paying more for porcelain tiles?

That depends how much more and how much you like the look. If on the wall, wear and tear means little.

(added to original answer):

Porcelain is harder and denser than ceramic tile. It will take more abuse without cracking, and can be used outdoors in harsh climates because it will withstand freeze/thaw cycles that ceramic cannot.

So your answer depends on how you're going to use it. If you're putting the tile on a kitchen floor or billiards room where hard things are likely to be dropped on it, then yes, porcelain is worth paying more. But if you're installing tile on a bathroom floor, where the hardest thing to hit the floor are plastic shampoo bottles, then no - the higher price of porcelain isn't worth it unless you just happen to like the look of your porcelain choice better than a ceramic choice.

There are different kinds of porcelain, too - which might make a difference when used outdoors or in rooms where there will be much heavy use. Some porcelain tiles have a dense gray body and a glazed color top coat; others are "color-through" or "color-body" porcelain - in these, the same color of the surface is the same color throughout. They cost more than glazed porcelain. If you chip a glazed porcelain tile, the gray body will show through. If you chip a color-body porcelain tile, the chipped area will likely be insignificant or nearly invisible.