Young also had three chances to beat Dallas and he only did it once, compared to Marino's 2. Who is to say he couldn't have done it.
Young's most dominant playoff games, with the exception of that gem in San Diego, came when he was watching Joe Montana.
I'm sure Marino would've killed for a receiving RB like Watters out of the backfield and Rice in the receiving corps like Young had when he won his one real SB.