Get the O.S. .12 The .15's are not as good. They tend to heat up more and wear out fast. They are bored oit .12's. Also ditch the PS idea, it should be called POS. I started with a PS and it was good for a little while then worked worse and worse. The started boxes are cool and you can get a nice one form tower (OFNA) for about 80 bucks with the battery and glow igniter included. I would also get the factory team truck form the start if you can swing the cost. You will spend lots more upgrading parts than if you just get it now.