It didnt have a door, I like doors, especially if they have leaded lights and a bell.Yak-9 was one of the better fighters of WWII. It was fast and maneuverable at low-to-medium altitudes, was available in numbers, and was reliable.
It had no CG problem as the P-39 did when the ammunition was empty, and was conventional gear, which was WAY better suited to Soviet airfields, and was more maneuverable in general.
It had almost twice the range of a P-39 on internal fuel. What's not to like about the Yak-9?