I forgot they added that. I doubt there’s any real difference between the two. At first I thought it was to pad out that era to give you more choices for the 6 plane requirement, but that era is spoiled for choice. Then I thought maybe the Marines did something to their Corsairs.
Apparently the Marines used it as a ground attacker and because they weren’t flying off of carriers, they just removed the hook entirely. The engines are also slightly different because the USMC carried more ordnance than the Navy did.
It’s all really minor stuff and I doubt it amounts to much difference ingame. The ingame plane can’t carry any ordnance either, just like the Navy F4U-1a.