I have used fresh, but I prefer canned. The process of canning them, when done right, provides a perfect product for a pizza sauce. You need no skin, no seeds, no jelly, and a cooking method that will not exceed 200 degrees. While that can be done, it is exceedingly time consuming to do at home for small amounts. Find a good canned tomato and save the fresh garden grown ones for uses that do not involve cooking, where the flavor will really shine.