When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Good luck and have fun at the track! Others may chime in and recommend the MM plates. They are a bit more expensive and may be better suited for track use. I really can't speak to that myself.
I imagine they're more expensive than J&M for the same reason their control arms or more expensive: they were the first on the scene and could get it. Having installed the J&M I've trouble seeing how MM could be much different or any better. The J&Ms can be installed in one of two ways one for street and the other to give more negative camber and it can be alternated in just a few minutes.