IMHO and experience, the type of ground meat you choose to use for meatballs depends on the kind of meatball and flavour you're going for! You can use anything from ground pork like I do here, ground beef like I did in this Gluten Free Meatball Recipe, ground turkey like I do in these Sun Dried Tomato, Spinach and Goat Cheese Meatballs or a combination of different ground meats (such as veal and pork) like my mama does in her famous Mini Meatball recipe. You can also use ground lamb, chicken, venison, bison... the list is honestly endless!