When my party splits up, I have more work shuffling between them.
When they're together, I can often just sit back and let them do stuff with minimal interference from me.
But we often wind up with two groups, even if there's only three players, and I try to bounce between 'em and keep things exciting.
Last night for a while we had the ninja failing to break down a cheap motel door, the gangster convincing his cronies to go give the ninja unwitting backup, and the rest of the group maintaining their cover story.
What disaffects you about the splitup?