Well, one of the secrets of the pro racing circuit that I recently discovered is that many of the factory drivers out there find ways to sneak Kyosho parts onto their cars. You get what you pay for with Kyosho. Durango makes some great stuff as well but they're still working the bugs out of their manufacturing process - evidenced by the quality of some of their plastic parts (check the forums for the DEX410/DESC410R). Kyosho's been at it for a long time and has the best reputation for quality. In the case of the springs you'll probably be good either way.