All of the recipes on this website call for the use of active dry yeast; mostly because it is generally easier to find.   My personal preference is to use instant yeast.  In terms of the quality of the final product, it doesn't really make any difference which kind you use.  The reason why I prefer instant yeast is because it doesn't need to be proofed and doesn't require being dissolved in water so you can just mix the yeast in with the rest of the other dry ingredients.  I also don't like cooking with hot tap water which I don't have to use with the instant yeast.

If you are using instant yeast for your pizza, the amount called for in the recipe will need to be reduced by 25%.  So if the recipe says to use a teaspoon of yeast, converting to instant yeast would mean using 3/4 of a teaspoon.