Quick answer
Use close-up magic when guests are mingling. Use a seated show when everyone can comfortably watch at the same time.
Why close-up magic works for cocktail hour
Cocktail hours are social by design. People arrive at different times, conversations start and stop, and the room is usually not arranged like a theater. Close-up magic fits that flow.
When a stage or parlor show works better
If everyone will be seated after dinner or if the event needs one shared feature moment, a short parlor show can be stronger than mingling magic.
What if you want both?
Many events can use both formats: close-up magic during arrivals or cocktail hour, then a short seated show later when the group is gathered.
For more detail, see Close-Up Magician NYC.