Airbnb

We use AirBNB often and yes always must pay upfront to AirBNB, who does not pass the payment onto the owner until you get there. Read the Terms and Conditions on when the money is actually paid to the owner and your right for dispute. Also pay close attention to the cancellation policy for that property, some are very strict. The good apartments go fast and it is not uncommon for us to book up till a year in advance, look at the calendars for properties and you will see how far out they are booked. Personally I like having my lodging paid for before I get there, one less thing to worry about.

For many reasons, I prefer to use a booking service that doesn't charge me in advance (I sometimes book 8 or 9 months in advance).

For example, Booking.com has a variety of price ranges; some propeties may list on airb&b and booking.com. I would check prices if the property you want is listed on both, and make the peace-of-mind decision. Note that both cancellable (is that even a word?) and non-refundable options are available.

I have only used vrbo.com for rentals over the past decade. I find them easy to deal with and have been happy with the apartments - so happy that I have rented the same ones over and over. My company rented through airbnb and even thought the apartment was gorgeous (despite some ikea furnishings), the price was way over what it shoud be. Even the owner told us not to rent through them again! I generally rent in January for July/August occupancy.

On our trip to Spain last March, we rented exclusively through Airbnb. I also like to have rooms paid for ahead of time. Less trips to bank machines. We had wonderful apartments with terraces and washing machines. In Granada we had a gorgeous apt with a huge terrace looking directly across to the Alhambra for $87 a night! You just have to pay attention to all the information and details listed, as you would on any site.
Btw, here is a link to the Granada apartment if anyone is interested. https://www.airbnb.com/rooms/4238597

Airbnb's process of cancellation is very customer friendly Unlike similar services

I have stayed in Italy at Airbnb places and also cancelled some I had booked there as well

Before you book the property's cancellation policy is clearly defined and will be followed to the letter so read carefully. This is chosen by the property owner so will vary per place

If you cancel you can do so with a click of the button and the process is automatic based on the terms of that policy so if you are within the timeframe of 100% cancellation you get your money back immediately ; though often the $50 fee or so for Airbnb is not refundable (this is also clearly stated)

In comparison vrbo or homeaway which I have also used:
When cancelling you need to do so with the owner and they need to refund the money back via the website ; as a renter there is no easy cancel button
Vrbo and homeaway listings are typically less expensive for the same property I assume the property owner pays more using Airbnb ; though security deposit holds are more common on vrbo and homeaway