OK, but that's a varietal difference, which is one of the factors that the poster identified as being important - no? Unless your parents are actually growing San Marzano tomatoes.
Yes, it's a varietal difference. Obviously there's some personal preference here, but California grown San Marzano-style tomatoes (not true San Marzanos as that's a protected designation of origin) can be just as good. Canned tomatoes also just taste better in some applications, like pizza, so they're always going to be better than GP poster's parents' home-grown fresh tomatoes.