Engineers vs earth's military: what would happen and who has the advantage

The Juggernaut and the Derelict are the only warships that we have seen in Prometheus and Alien. But what is their military is even composed of, do they have a organized/functionally army and navy, and what of their weapons? Do they have Rifles, rocket launchers, or machine guns? Or an Bio-energy based weaponry? And what would it happen if a human organized military like the U.S Colonial Marines ever encountered the engineers, and how would both sides react with different weaponry and tactics?? And how would their training be compared to that of a human.