airbnb is useful particularly in cities, but that's also where warmshowers has most of its members. I've used airbnb several times, but only once on a bike trip. The one time I used airbnb on a bike trip it was enormously helpful, because I needed a place for 4 nights. I would never attempt to impose on a warmshowers host for 4 nights. My friend and I found a 1 bedroom apartment with a secure place for bicycles, for much less than a hotel room would have cost us.