The in game toughness values seem to be the same for both planes.
I don't know about the construction IRL, but the Ki-43 is known for structural failures while the Ki-27 is not. Well, that is as far as I am concerned. The Ki-43 did not have self sealing fuel tanks, the Ki-43II did get some sort of fuel tank protection.
It could be noted that the Ki-43 is sleeker than the Ki-27, which would make the structure higher stressed.
All in all I wouldn't be surprised if the Ki-27 was a bit tougher, or maybe "less fragile", than the Ki-43 in real life, but I don't think it is that way in game.
|