Against the La7, Spit IX, and N1K2 the 109G6 may as well be the same plane as a 109F4. Except it has those hideous tumors on the nose.
Actually thats not quite right.
109F4 vs La7: La7 is faster, accelerates and climbs better, has more firepower, rolls better, turns worse.
109G6 vs La7: La7 is faster, accelerates and climbs better, has more firepower, rolls better, and turns better.
109F4 vs Spit IX: Spit IX is faster except right on the deck, accelerates and climbs better, has more firepower, rolls better, and turns better.
109G6 vs Spit IX: Spit IX is slower till 10k or so, accelerates and climbs better above 10k (below 10k the G6 has a very slight advantage, slight enough that it isnt even noticable in my opinion), has more firepower, rolls better, turns better.
109F4 vs N1K2: N1K2 is about the same speed till 10k (then it gets slower), accelerates and climbs about the same to 5k (after that it drops off a lot), has more firepower, rolls better, turns better.
109G6 vs N1K2: N1K2 is slower, doesnt climb or accelerate as well, has more firepower, rolls better, and turns better.
Really, the only difference you'd see in switching to a 109G6 is that you would no longer be able to out-turn La-7s, but you could out-run N1K2s a lot easier. Well that and the DD's sitting on the nose.