I dunno, they both have their ups and downs, Granted the warrior will last him longer, and you already have a working knowledge of it's quirks, and probably a few spare parts lieing around. But it's a bigger quad both power, and size wise, size will make it him feel like the quad is pushing him around, not him really riding it, and throwing it around. And on top of that I'm not sure how your son is, and if he get's a lil panicy and gooses the throttle when he panics that's a lot more power shovving him into the trees and such.
But for the blaster, It won't last him as long, but he won't have to grow into it as much if any at all, it's power can be touchy w/ the power band, and if he's not used to that and pops into it at the wrong time it could come up and over onto him (I dunno about you guys but my friends blaster is easier to wheelie then my warrior), and some parts will be interchangeable, not many though, simple things like tie rods, and tie rod ends are. But 2 strokes can be more work, if not tuned right, and preventative maintnance is done regularly. Though the size/weight thing is also in his favor on the blaster. Other than those I can't think of anything that would make you look at one more favorably than the other.
Over all I would say look at the warrior if he has some of a feel for it from riding yours, and if he is big for his age, and I would go with the blaster if he doesn't have experience on yours, if he has a small frame for his age, and doesn't mind joining you in the garage to wrench on it, since it will be his. ;D
~Bill
