The only thing they share in common is that they are V6s, have the same displacement, and both use common-rail injection by Bosch.
Mercedes makes their own engines. The 3.0L V6 is engine code OM642, and it has been around for a while now (2006). Cast iron block, very different layout of engine components vs the Motori engine. Good workhorse of a motor. If I were to guess, I'd say the Merc OM642 is a more durable engine.