Hi Andery,
My opinion are :
1. How much your project budget? Which is more cheaper, the cooper or the aluminium.
2. How long will be the distribution length for the power cable to serve the load. How much the voltage drop you have calculated as for cooper and the aluminium?
3. If the voltage drop that you have considered into account and the project budget you may have the guideline which one to choose. As we know aluminium is considered cheaper than cooper, but in term of voltage drop and induced current, cooper conductor is more preferred.
4. How you install underground cable. Basically, underground cable is installed by common method used in worldwide. The parameter such as the deep of the trench, protective slab, maybe different.