Like a_in_the_b and pitino mentioned, besides the obvious player skill and the system you run the key to all of these "which player" questions is often the rest of the team: What are your other players giving you, or lacking(particularly those in the same recruiting class)? Project what your team will look like when the recruits are upperclassmen. Will the team have scoring, but not enough rebounding? Will the team have defense, but not enough passing? SFs are often good for this because you can find a wide range of skillsets at that position and plug any holes that you might have.
Unless there is a clear difference in player quality it's usually good practice to pick the guy that best complements your other players.