Well, it all depends on what you're after and what you want out of it:
a) Is it holiday home or investment? b) What kind of budget you have? c) How risky do you want to go (although most areas in morocco share the same risk profile) d) How long do you want to hold your investment for? e) Finally, are you looking at earning money out of the rental income or just waiting for capital growth?
As you can see, its not just as easy as saying which area is the best. Having said that, this is what I feel:
Fez: Relatively new market and property prices are very cheap. Tourist numbers are not that great as Marrakech or Tangiers, so will take time for rental to pick up. But capital growth is projected to be excellent. Prices here start from Â£20k to Â£30k
Marrakech: Arguably the most popular touristic area in Morocco and held in high esteem by certain hollywood stars as well. So needless to say prices here are probably the most expensive in morocco. Capital growth may not be as great as other regions of morocco, but still quite stable. Rental could be really good depending on the type of property. Prices average around Â£200k plus for decent properties.
Tangiers: The coastal region is very popular and in heavy development. Large scale developers like emaar and fadesa have moved aggresively into the area, and its set to become a tourist hotspot. Rental projects are quite good and certain properties on resale market are selling as well. Prices here start from Â£60k for decent location units.