The only thing that annoys me the Airbnb booking experience, is that it's not really a booking, it's putting in a booking request and then waiting for the owners to approve. Compared to regular hotels.
I the prices kept changing at different views, I couldnt save a search, even active searches would just go away if i tapped back, they pushed me to link to a third party auth, but when I did they created a separate account and i could no longer reach the one that had my reservations. It was a mess all the way around.
The only thing I did like was all the weird places to stay.
While AirBnB might be pleasing on the eyes, Booking's UI is optimised for conversion. The benefit of "better UI and UX" is arguable here if it does not result in more $ for the business. Specially if they want to compete in the public market.
Disclaimer - Ex-Booking.com employee
Also, If you have not tried, I'd recommend giving the (android) app a go, bias aside, its one of the smoothest look-to-book experience I've had.
Regular hotels might not always be a live booking either. Every once in a while, someone misses a fax. Usually a real hotel has some slack to fix things when some one comes in with a reservation that didn't get booked.