Long story short:
I think the “unique tap water” story is nonsense too regarding NY style pizza.
I think the use of San Marzano tomatoes might be “a secret” to infinitesimally improve your result at a very high level, but it works only together with many “other secrets”. You know, you need pennies to make a billion.
Conversely, if I take a person who has never eaten any cheese and I give them a daily fresh artisanal mozzarella from Battipaglia AND an industrial mozzarella di bufala, they won’t believe they tasted the “same product” obtained by the “same animal”. That’s too much different, like, say, comparing an apple and a peach.
Long story... long.
The “tap water story” is not completely nonsensical, but maybe it is in regard to NY pizza dough. You can imagine how many times I’ve heard the same story about the importance of local water in making typical italian bread or anything else. I strongly believe that minerals in the earth and water can be very important in making wines and oils, but I have my strong reservations about a pizza dough.
Nevertheless… there’s something I would like to say about a very special “fast food pizza style”. It is called focaccia genovese, and it is obviously from Genoa.
This is it:
Yes, no topping. NO topping. I don’t know how, but they can make it SO delicious that everybody loves it. You are supposed to eat it alone, with nothing else, at room temperature.
In Genoa you can stop at a random bakery and enjoy it. I could eat tons of it. In Milan, which is 1 hour drive from Genoa, you have a hard time in finding a decent focaccia. You take two bites, then “ok, enough plain bread for me”. Why? That’s the same oil, the same flour… Is it water? Technique? Magic? I don’t know.
Speaking about tomato on pizza… Can a San Marzano make a difference? Yes and no.
If you are using a very low quality tomato sauce, then any San Marzano sauce would make a difference, because it’s a certified quality product, and it is known that San Marzano is ONE OF THE KIND of tomatoes more suitable for sauces.
But if you use quality products, you can achieve top results using any other kind of sauce-breed tomato. Anyway a certification of origin gives you just an idea of a benchmark which is a MINIMUM level of quality. You can often find uncertified products which are better, but not guaranteed.
I dare anybody to recognize a San Marzano from any other tomato just at tasting. With mozzarella di bufala it is different, as I mentioned.
Fun fact: tonight my father invited me to a quick “blindfold tasting” of Genepy (a herbal liquor from the Alps). We tasted a homemade one, an artisanal one, a premium (riserva) commercial one. He wanted to play a joke to one of his friends, and poured him the same product 3 times. He had no clue, and made a complete review, underlining differences, pros and cons. And stated the second one was the best.