Hi there
I had the P40 and my father owns the Spitfire. Both fly incredibly good, you can't go wrong with those Kyosho warbirds! I guess you will have to decide, which one looks better to you, and then buy the one you like better.
My father flies the Spit with a OS 81FS-a. There is way too much power, you have to land on grass, otherwise she will never stop taxiing. Now he is thinking about putting a "pre-glow machine" in (I dont know the word in english, sorry. He just wants to set the idle-rpm lower). I guess a good motor for the spit would be a OS56Fs-a. The Spit flies great, like all Kyosho warbirds do. We think there are no negative points.
I owned the P40. Unfortunately it crashed the other day because the elevator fell off

. I flew the P40 very much and I can tell you it is also like the spit a great flyer! The rotating retracts worked perfect until the end of my P40, you don't have to worry about them. The only negative point at the P40 is that the colours of the cowling and the fuselage dont match. If you stand right in front of the plane you see it, but in flight it is hard to see.
I flew the P40 with a Hacker A40-14s with a 13x8 and 5s 5000mAh. I guess this is a perfect setup for those Kyosho warbirds. Now I'm thinking about getting the Hien, it looks pretty good!
I'm sorry if something may be hard to understand, here in Switzerland it's late and I have a hard day behind me
If you have any questions, please ask. The more I write, the more my english improves

(I guess it has to improve a lot

)
Regards
Stefan