So I am looking to upgrade the radiator on my FD and I can purchase a 2 row copper koyo here locally or I was planning on ordering a 2 row aluminum koyo via rx7store.net is copper better or is aluminum better? Thanks.

 

copper is a better conductor so it will discharge and absorb heat faster than aluminum but it is also softer ( so the fins will bend easier) heavier and a more expensive metal. I personally like to use aluminum since it has always handled my cooling needs so far ,its also tougher and cheaper.