Lol.
Both gameplay and the amount of P-51s you see in the game.
You have seen the kill stats on those planes, haven't you?
It was the most famous plane of WW2 for a reason.
Super fast, great guns,range, great visiblity, carries plenty of ord.
And contrary to popular usage, its pretty manuverable too.
I say perk it!
I've seen worse arguments for perking planes, GVs etc in here.
just my opinion.