Castrol synthetic or Valvoline?

I know the thread is a couple weeks old, but I'll put in my .02. I've use Mobil 1 in my race car and street cars and have never had an oil related failure. My last two cars have used it from purchase to grave. My '01 Ranger had 273,000 miles on it before I totaled it. My current ride is a '10 Dodge Caliber and it's getting ready for the 130,000 mile oil change. The Ranger used 5W30 and the Caliber uses 5W20. The filters have all been Purolators. I've changed the oil every 5000 miles without fail. I'm looking at doing a stock style rebuild on a 360 with a mild roller cam. I'd have no issue with running a 5W30 synthetic (EFI engine). Just a note...VW is a big believer in Castrol Synthetic...from Germany. I've heard the same regarding Castrol in the US not being a true synthetic. I'd make my oil choice based on your cam (flat or roller). I've also heard a lot of good things about Brad Penn.