I think what stavs is looking for is a global overview of the different tomato types, processing and when you might use one or the other. I will take a stab from this approach.
Basically you have two main groupings of tomato.
Fresh - Fresh tomatoes are typically used in pizza Margherita, Foccacias, Sicillian styles, etc., where they are typically laid out in whole thin slices. They can be in chunks, depends on taste. Many say if you want a traditional pizza, this is the only way to go. Also, some people use sun-dried tomatoes as well. This isn't a fresh product, however it gives a more concentrated tomato flavor without sacrificing much flavor. Fresh tomatos typically contain a lot water, therefore they are used sparringly, even sometimes being put on AFTER a pizza cooks. The fresh tomato of choice for italian pizzas is the Roma, most notably the San Marzano. This tomato is known for a high pulp content and low water content. A pizza using Roma tomatos will be far different than using other larger tomatos, such as early girl, big boy, etc. as those contain much more water.
Canned - Within the canned category there are about 3 main types:
1) Canned tomato sauce, paste, puree
2) Canned tomatos (Crushed, chopped, whole.)
3) Prepared "pizza" sauce.
1) Canned tomato sauce - Within this grouping there are further categories to think about. Typical tomato sauce and paste you get in a grocery store (Contadina, Hunts, Del Monte.) is processed with HIGH HEAT. These products typically have less tomato flavor and taste "acidic" or "canned" to most people. If you are using expensive flour and cheese, this is probably your worst choice for a sauce IMO. The more difficult "Premium" brands of sauce are processed under LOW HEAT or NO HEAT conditions and are "vacuum evaporated". This process concentrates the tomato product while retaining freshness. This includes some brands like 6 in 1's, 7/11, Stanislaus, Etc. These typically have a more "tomato" flavor and usually aren't so bitter, which is why many people prefer these premium brands. In either care, you will have to season the sauce (although some just use it as is), with either fresh or dry herbs, then typically let it sit overnight in the fridge to let the aromatics do their thing. If you use a premium brand for it's freshness, typically you do not cook your sauce, as heating will inpart a different flavor to the tomato. This however is just a matter of preference.
2) Canned tomatoes, whole, crushed, etc. - The same thing applies in this category as above. There are regular store varieties processed with HIGH HEAT, then there are the premium brands which typically taste more "tomatoey". The thing with this group is that you have a chunkier product. This is more recommended towards Chicago styles where the pie is really thick. This however is still a matter of taste. With these products, you have the option of draining off the water, meaning you can have a relatively "fresh" whole tomato taste, without having to use fresh tomato and dealing with the mess.
3) Prepared pizza sauce - These can be either HIGH HEAT or vacuum evaporated products. The basic premise here is that the sauce is usually ready to go out of the can or jar. Typically it has basil or some seasoning in it. You may also wish to add more seasonings to it. Manufacturers of this product target commercial stores since it allows them to just purchase product and use it. If you want a more "commercial" taste, then this one is for you. These sauces are also usually judged by their solid content. The more solids, the thicker the sauce and typically the more "tomato" taste. These sauces also have the best "sticking effect" when put on a dough, as opposed to just fresh crushed tomato, which would not stick to the crust that well.
I have seen people mix and match different varieties. That is to say, take a prepared pizza sauce and dump it in some 6 in 1's. The idea here is to produce a flavor you are happy with without compromising the texture. Your sauce should be flavorful, yet ammenable to the style of pizza you want to create. I would suggest you think about pizza you have eaten which you really like, then try to find a sauce that suits your taste. If you mention a style here on the boards, someone will be able to tell you which types of sauce they would recommend. Good Luck!
