Pettitte and Santana are polar opposites, and both have merit for debate. One guy was a workhorse for a long time, while not being overpowering or spectacular.
Santana was the most dominating pitcher in baseball for about a 4 year stretch, and then got derailed by injuries.
These are all guys who will be debated. Whats better, a guy who wins back to back Cy Young's and is completely unhittable for a short time, or a guy who plays for 16 years and is always steady adn reliable.
I don't think either are HOF'ers actually. Halladay maybe, Pettitte maybe, Santana no