Slot canyons are famous attractions in the Southwest. The most popular and impressive ones may be the Antelope Canyons. Please be aware that there are 2 separate canyons: the Upper and the Lower Antelope Canyon.
The tours offered by different trip organizers in the Upper Canyon do not differ much. Typically they arrange the transport from downtown Page by special trucks, transporting 10 persons in a fast ride. This is also the group size for the trip through the Canyon.
Visiting the Upper Antelope Canyon has unfortunately become a massive mass tourism activity. You are driven through the Canyon, positioned in places that allow good pictures; to accelerate the walk, the guide may even take the picture for you. We even experienced a guide modifying the settings of our camera which did not work well afterwards and which could not be repositioned to the previous settings due to time constraints. Although we selected the more expensive tour at noon we did not see any beams.
In the Upper Canyon you go back the same route but are not allowed to look or take pictures when going back: Hurry up! This is mass tourism at its worst – although the views in the canyon are of course sensational and worth visiting.
The Lower Canyon can be reached by your own car and in our case the trip was a bit less hurried than in the Upper Canyon. The Lower Canyon is also very beautiful and worth visiting; we did not find major differences to the Upper Canyon. You have to manage a few ladders which are no problem for reasonably fit persons. You walk through the canyon only in one direction which allows an interesting look to the small slot from the surface at the end of the walk.
Both canyons are very impressive. The Lower Canyon is less crowded and may be your preference if you decide to visit only one of them. Its visit is also a bit cheaper.
Furthermore, there are many other slot canyons which are almost not visited and their visit is more adventurous than visiting the Antelope Canyons. Let me only mention the Little Wild Horse Canyon near the Goblin Valley State Park, the Peek-a-Poo Gulch in Escalante, or the Slot Canyon in the Anza-Borrego Desert. However, check whether you need a 4WD with high clearance to reach some of the less visited slot canyons.