Wilwood fluid is a bit more expensive. I buy it at a local speed shop, but it's readily available. I use wilwood in the clutch for two reason - the clutch line receives the most heat from the header and, IMO, the clutch is most critical, when it's gone it is gone.... whereas I have two sets of brakes (front & rear) to fall back on.
Maybe not the best reason, but that's my story and I'm sticking to it.
http://www.raceshopper.com/wilwood_brake_fluid.shtml
http://www.exoticperformanceplus.com....html?item=864
http://www.wilwood.com/Products/006-...-EXP/index.asp