Southern Air Temple

The Southern Air Temple, also called Jongmu Air Temple, differs from the others in the way that its roofs are blue, instead of green. This is where Aang grew up and learned to become an airbending master. Monk Gyatso, Aang's mentor, also resided here, and a statue of him stands at the entrance to the temple. This is also where one of the last winged lemurs, Momo, was found.
Northern Air Temple

The Northern Air Temple differs from the others in the way that it is a compilation of what most of the other air temples are. It has green roofs and is on a single mountain. After almost-extinction of the air nomads, a group of earth kingdom people have occupied the air temple, who made many technological advancements. However, they use to help them to help the fire nation make war machines out of fear. Eventually though, they fend off the fire nation and just try to make the world a better place. Although their practices go against the normal air nomad culture (creating pollution and disturbing nature), they make things better for those who are disabled.
Eastern Air Temple

The Eastern Air Temple differs from the others in the way that it is on three mountains instead of one. There are bridges and things that connect them to get from one temple to the other. Avatar Kuruk, the previous airbender avatar, was born and raised here. This temple was damaged the most during the Hundred Year War. Appa was born and raised here too. I don't know, a homeless man inhabited this area near the end of the Hundred Year War.
Western Air Temple

The Western Air Temple differs from the others in the way that it is on the underside of a cliff, instead of being on a mountain. However, it is still, supposedly, inaccessible to those without sky bison, until the fire nation wiped them out. The buildings look upside down, with the roofs being the floors, and the floors being the roofs. There are waterfalls from the hanging buildings, giving a very nature-y feel. There are also metal doors in case of attacks, so it's more technologically advanced. Actually it doesn't really say if the other temples have similar defenses, but they aren't shown, so we will assume that the Western Air Temple is special in this way too.