Front: I assuming you front extention with RC is without renovation permit, else only half on it will need to work on. Than it will depend without with roof tile better view that RC slap.
If could use Roof tile, 1) Nice 2) RC is more hot 3) Maintainance more ease if any leaking, else never ending story.

For back, if you didn't inteed for future extention to second floor, than use roof tile , just imaging the RC on top and hot air coming down to Kitchen. If unsure than you better informed you contractor that you may plan future expention and you like the roof to be RC or tiles. So that when you extention take place you could just remove the tile and build slap across...
But RC you will need carefull on leaking issus