Errrrr. Yes of course it matters. Depending on the map of course.
funnily enough, I'd no prior knowledge of what map you were going to buy
but, if you're just using the GPS one it really won't make much difference, it'll only come into play if you need to relocate yourself using the GPS and the map in which case it will be handy. In that case, the answer was the standard one, it's the datum written on your map.
In answer to your question, there is no datum for Morocco as there's no national mapping. By and large maps are at 1:4,000,000 scale, with the exception of the popular Toubkal area, and produced by the French or Russians some years ago. In a lot of areas given the low cost it makes sense to employ local guides, there's no particular virtue in wandering around the desert navigating with a road map.