What is the legal test for determining whether a motion for dismissal should be with or without prejudice?

Some cases have simply assumed that the district court will conduct a hearing after a remand to determine whether dismissal should be with or without prejudice. See, e.g., United States v. Tunnessen, 763 F.2d 74, 79 (2nd Cir.1985) ("there is no need for a hearing [on remand] ... because we conclude that a decision to dismiss with prejudice would be an abuse of discretion"). But see United States v. Russo, 741 F.2d 1264, 1266 (11th Cir.1984) (district court initially determined issue of prejudice on remand without a hearing, although evidentiary hearing was later conducted following grant of petition for reconsideration).