The main differences are size and atmosphere. Most pousadas have fewer than 20 suites and they are all individually owned and managed, so have their own personality. All pousadas here have clean and comfortable rooms with en-suite shower facilities, so in that sense they are like hotels, and there will often be a fridge stocked with cold drinks. You may even find wi-fi internet, but you won`t ever find 24 hour room service, or a business centre!
