Please advise. On the way to Marrakesh where is it better to stay overnight? Why? Thanks!

Coming from???
You not need to decide it now, or? Go to Skoura, if you like the oasis, stay there. If not, continue to Ouarzazate.
The best place to overnight is Ouarzazate, as Skoura is quite in the palmerie and calm in the night, so Ouarzazate would be much better to enjoy your night.
oh, we loved the palmerie..would have stayed there longer, had we known how wonderful it was there. les jardin de skoura..nice grounds, wonderful hosts...i would go back in a second.
Hi
Skoura is very little and quiet, nothing but a view houses, some palms and the beautiful Kasbah Amridil to see.
Ouarzazate on the other hand offers a lot, beautiful Kasbahs, film studios, film museum, nice restaurants, shops, oasis, the lake etc.
My advice would be, visit the Jardin de Skoura and the Kasbah Amridil in Skoura and then continue and stay overnight in Ouarzazate, which offers a wide range of hotels.
Have a great trip.