The Granite is an upgrade over the smaller Diorite and uses a command module to control the reactive armor. It has two standard modules, instead of one. These can be used for transporting supplies or personnel safety through unstable asteroid belts.
The larger vehicle size also allows it to support double front armor. This allows the vehicle to take multiple impacts from the front. Previous vehicles were left exposed after a section of the reactive armor was activated. This extra armor allows the Granite to go further into chaotic asteroid fields and stay in the field longer before having to return to base to be refitted.