What is the perk cost on 38's now ? 
^^^^ hlbly was too obtuse, it appears. P38's still have cannon.
But you're missing the point. The challenge is to win fights when you're not in the best turner, or the fastest, or armed with cannons. Sure, P38s have cannons, but that's to compensate for the "shoot me" sign.
Otherwise, it's all about style. You'll always look stylish in a P51 or P38. Hellcats and Jugs grow in beauty over time. Just like wearing the black tux, you'll always look your best in blue and bentwings.
HONK!
Gooss