The MPT 5 is a good tyre but the side lugs are quite aggresive for sand, the XZL will perform better on road and on sand, will give a longer footprint,(flexes better) will run cooler and last longer.
It and the XS are probably the best tyres, the XS is too sand biased and wears quickly, the XZL is diffucult to beat - thats why nearly everyone (with Trucks) uses it.
If you are heading to West Africa, try Michelin Dealers in Spain for a good price.
'95 LR 90 300 Tdi
'02 KTM Adventure 640
Ex Rockape, Ex Drago
...and Bloody Nice Bloke!