I imagine a major difference is that most vacation rentals are rented out by the owner of the unit, whereas it seems like a lot of Airbnb rentals are being offe

I imagine a major difference is that most vacation rentals are rented out by the owner of the unit, whereas it seems like a lot of Airbnb rentals are being offered by tenants who are under existing rental agreements (which likely stipulate they can't sublease without permission from the landlord).