The short answer
Choose by time. With one free evening or a single night, choose Agafay: about 40 minutes away, with camps, camels and Atlas sunsets but no dunes. With 3 days or more and a wish for real sand, choose Merzouga. Choose Erg Chigaga if you have more time still and want the quietest dunes.
In more detail
The two are sold with the same words, camps, camels and sunsets, but they are different trips. Agafay is a stone desert about 30 km from Marrakech, reached in a normal car. Merzouga sits beside Erg Chebbi, a true dune sea with sand rising to around 150 m, roughly 560 km away over the High Atlas.
Agafay suits short stays, families with small children, and anyone who wants a desert dinner without giving up days of a city break. Merzouga suits travellers for whom the dunes are the reason for the trip, and it repays the road: Aït Ben Haddou, the Dadès and the Todra gorge come with it.
The camel ride differs too. In Agafay it is a short ride over rocky ground. At Erg Chebbi you ride across real sand to a camp in the dunes, and you can climb a crest for sunrise. Stars are good in both, darker in the deep desert. Doing both is common: Agafay as a gentle start, the Sahara later.
Good to know
- One evening free: Agafay sunset and dinner.
- One night free: an Agafay camp.
- 3 days or more: Merzouga.
- 5 days and you want solitude: Erg Chigaga.