Start with habits
If the tub is used for storage, a roomy walk-in shower may serve you better. If someone loves a long soak, keep the tub.
Think about small children
Families with young children often keep at least one tub in the house. The hall bath is usually the right place for it.
When both fit
In a larger primary bath a separate shower and freestanding tub can share one wet zone, which keeps tile and glass simpler.
