In real life the G-6 was a better fighter than the G-2, but the improvements does not easily translate to a simulation since they are mostly instrumentation/pilot aids, reliability and structural changes. The upgraded fire power is really the only benefit that we get in the game. The all-out performance suffered slightly due to increased weight, but more so because of increase in drag from the cowl bulges, wing bulges for the new stronger gear, and fixed tail wheel (the G-2 has a retractable one).