This is my analysis.

If we get Shinji we get rid of a rleatively useless player as well as a player who seems to be Mafia. Regardless of the results, we can capitalize on them by finding on the truth of Jin's statements. From there, we can be sure of Gin's claims in addition. This will give us an idea of two players' identities. Though I really want to vote for Ulquiorra, Shinji makes more sense strategically.