The distance between Marrakech and Merzouga‘s Sahara Desert is 563 km, it takes around 9 to 10 hours (Non-stop) in order to drive the 350 miles across the Atlas Mountains.
It’s quite popular destination, located in southeastern Morocco. Moreover, it has magnificent orange sands and huge rolling dunes that you’d expect from the Sahara, even though it’s so far, you may choose to break up the journey with an overnight stop in Dades Gorge along the way just like most of the travelers do.
In regard to Marrakech and Zagora’s Sahara Desert, it is 351 km, it takes around 7 hours 10 minutes to drive the 219 miles across the Agdez’s Draa Valley.
In addition to that, its desert is extremely rocky and has much tinier dunes than Merzouga but perhaps your duration stay in Morocco is quite short, thereafter it is best option for you.