Better low rpm performance than direct injection. Cools the air prior to the combustion chamber creating a more dense mixture making it more efficient at low speeds. Direct injection at low speeds can add to the problem of oil/fuel dilution in the crankcase if run for short periods of time. Once temps increase with RPM and load, direct injection cools the air inside the cylinder allowing for higher volumetric efficiency, precise fuel metering while preventing detonation. Gives you a limp home ability as well should something happen to your high pressure pump. Having both really is the best of both worlds, it also means you have two injection systems to maintain.
