As guests, we tried out Airbnb for a late-summer jaunt to upstate New York to try something more informal, cozier and hopefully cheaper than a Holiday Inn or Hilton. It worked out.
We stayed one night in a wonderful farmhouse of a couple whose kids have left for college ($85 per night for a large room and our own bathroom). Another night was in a cabin on an old family chicken farm ($125 per night for a cabin that sleeps four). A Holiday Inn in the same area runs $100 to $150 per night for two people, and you probably wouldn't share wine and travel stories with other guests in the lobby while a little old dog scurries around your feet.
Airbnb's commercial transaction removed a level of uncertainty from our trip, but it added a layer of formality and distance that didn't exist with Couchsurfing. Take the simple act of sharing a drink with your host or guest. One of our Airbnb hosts politely demurred, while our Couchsurfing guests were usually game for a beer or three. But just try inviting the hotel concierge up to your room for a glass of wine and see what happens.
Which site to go with depends on what you want out of an experience. Both, and others such as the long-running vrbo.com (Vacation Rentals by Owner), offer an alternative to traditional hotels and a chance to dive into life as a local. In San Francisco, where Airbnb is based, the company recently launched "local lounges," established coffee shops where Airbnb guests can stop in to get a welcome and a travel guide.
On Airbnb, the focus is on the accommodation. The best listings will have plenty of photos and reviews from other users. Couchsurfing profiles, meanwhile, read more like dating sites (though the rules bar using the site as such) or a place to find random new friends. You add photos and other users as friends. You can flesh out your profile to include musical tastes and life philosophy (my husband "would much rather try something stupid, dangerous or bad for me than risk feeling regret over missing out on something at the end of the line." I married the right man).