Using Canned San Marzano Tomatoes Vs. Regular Canned Tomatoes
San Marzano tomatoes are generally preferred for Italian tomato sauces because they are denser, fruitier, have a slightly lower acidity, and break down well when cooked.  I've made both fresh and fresh-cooked tomato sauces from the San Marzanos my mother-in-law grows, and would prefer these over just about any other tomato variety for sauce-making (dry-farmed Early Girls are also pretty good).

However, in my personal experience trying several of the canned and boxed varieties of San Marzanos available to me, they're not worth paying more than double what more common varieties of tomatoes cost.  For example, last week I made my standard "quick tomato pasta sauce" using boxed San Marzanos, and did not find it notably better than other high-quality boxed tomatoes (such as ones from Pomi) which cost $2 less. My judgement is that many of the qualities which make them a superior tomato when cooked fresh are destroyed in the canning process.

On the other hand, you're comparing them to Contadina, a rather low-quality brand.  Given that specific comparison, I would expect the San Marzanos, even the mass-market Italian brands, to be notably superior in quality.  So if that's your actual comparison, I would say go for the San Marzanos.

According to an article in Cook's Illustrated from several years ago (CI archives are behind a paywall, so no link), this is partly because San Marzanos, like other imported tomatoes, need to be canned at higher temperatures in tomato puree instead of at lower temperatures in tomato juice due to obscure US produce import restrictions.  So it's also possible that canned San Marzanos can, in fact, be excellent, just not the ones commonly available in the USA.