It depends.
In my experience, the average can of San Marzano tomatoes is "better" than the average can of Roma tomatoes. With canned tomatoes, so much depends on the specific batch and brand.
San Marzanos are prized tomatoes because they contain fewer seeds, are less acidic and have better flavor. However, this isn't always the case. I've gone through my fair share of mediocre San Marzano tomatoes.
Also think about what you're using the tomatoes for. For a New York style sauce, I won't use San Marzanos, but for a Neapolitan sauce, I definitely will. For a nice marinara sauce, I could go either way.
In my experience, The brand of San Marzano tomatoes is key. Cento, certified San Marzano whole tomatoes taste really good right out of the can with no additional salt or sugar needed. Of course this is a taste preferance that may be individual in nature.
- Mark over 4 years ago