Depends on durability and health of each player.
If the pitcher has a 29+ durability, he is a Cy Young candidate every year.
If the RF has a durability of 90+, he is an MVP candidate every year.
If the pitcher has a durability of 23 or lower, you will need to push him hard to get 200 innings out of him.
If the RF has a durability in the 70s, you will need to watch his rest carefully.
Obviously, if one of the players has very low health, you may need to choose one over the other. There is nothing more frustrating than a player that gets injured every other season. Especially if they get injured during development.