I bought a small cheese pizza at each, since I heard they were two of the best and tried them at the same time:
Santarpio's: $10 for a 14-inch. Very flavorful (ie. probably high fat cheese), with a garlic presence, the cheese obviously a blend (I detected romano). The crust was really bad, very tough, it must have been a poor crust day. It came with a small char and had been dusted with cornmeal.
Pizzeria Regina: $9:32 for a 10-inch. The crust on this was very tender compared to Santarpio's (dusted with flour instead of cornmeal) and easy to eat. There was no char. The cheese was oozing about, but nowhere near as full of flavor as Santarpio's. I didn't detect any strong garlic or herbs, and it appeared to be topped with only mozzarella instead of a mix, but I could be incorrect. The sauce seemed to be the same as most other typical pizzas I have had, nothing that stood out at all.
The superior pizza to me was Santarpio's, as it was extremely flavorful compared to Regina's. It was also bigger to boot for the money. I hope the crust was just off the day I had it, because it was very tough, you had to yank it apart.