The handling in FFXIII was awful because you were stuck with only two characters for a large part of the game. At least in FFIV you had 4-5 characters in your party the majority of the time.

In FFIV I didn't really notice that getting a 6th member meant someone had to leave the first time I played it. On subsequent playthroughs I already knew what happened so it didn't matter.

I will agree that the handling of the reasons for splitting up were better in XIII, though not as fun having one of your characters jump from your airship with bombs strapped to his chest.