I use both 6 and 1 and tomato magic a lot. They are indeed VERY similar. 6 in 1's are a little thicker and dont have the "tang" you get from the citric acid in tomato magic. Some might lead you to believe that citic acid is a bad thing, but I actually think it can help in some instances. If I am using a sour dough culture I definitely go for 6 in 1's because the dough will provide a little tang. If I am using commercial yeast I like that the tang tomato magic has beacuse it combines with the fatty cheese ant toppings in a nice way that I think is desirable.
All I add to either of these is fresh basil, and a touch of olive oil, but you could of course do the standard "american" pizzeria thing of using garlic powder, oregano, etc.... I feel like I get enough salt from my crust/cheese that I dont need to add salt to either of these products. I do ad salt to Italian tomatoes, however, which are usually packed with much less salt than california tomatoes.