One trip, several bags, whether that's one per traveler or one per type of luggage. Keep them all straight without losing the overview.
A bag per person or per suitcase
Create as many bags as the trip actually needs, assign items to whichever one they belong in, and see at a glance what's going where.
Still one shared list
Splitting into bags doesn't split the trip into separate lists, it's still one shared view, just organized by where things physically go.