Here are the cases where I have found airbnb better than any other site (and I do a lot of price comparisons etc);
- Fire Island NYC or small town Alaska, places that don't really have hotels and all lodging is room-shares in houses.
- Weird lodgings (e.g. houseboat in tahiti, tree house, school bus, teepee, bubble-tent etc - anything out of the ordinary where staying there is an experience in itself)
- Hongkong where hotels are typically expensive (this was before their crackdown, I've heard airbnb is not allowed or in grey area now)
- London where hotels are typically expensive, an airbnb will get you a private room / shared bathroom for much cheaper in some random house.
- Towns where all hotels are boutique hotels (smaller towns without a chain hotel footprint)
But 95% of the cases, a typical hotel is good.