The reason you don't see every Hog pilot flying F4U-4s is because there IS a perk. The reason you see far more Typhoons is because the Typhoon is NOT PERKED.
If the F4U-4 were to ever be unperked, the only Hogs you'd see would be -4s and the occasional Charlie. The F4U-4 IS THAT GOOD.
In regards to the La-7:
The F4U-4 is faster above 10,000ft, and on the deck is not all that far behind.
The F4U-4 is ouright superior in practically EVERY aspect of the flight envelope above 10,000ft.
The F4U-4 turns better, especially with flaps.
The F4U-4 zooms better, and sustained climb where the La-7 holds an advantage is significantly less important in combat.
The F4U-4 has IMO the superior guns (the 20mm are powerful, yes, but the Russian guns have awful ballistics properties).
The La-7's advantage in acceleration is within a second at best, so almost negligible.
The F4U-4 has greater range.
The F4U-4 has greater ground attack capability.
The F4U-4 has a much larger bag of tricks it can pull from in a fight than just running and HOing everything in sight.
Would I love a free F4U-4? Hells yeah I would. But there's a good reason she has one.