Castrol synthetic or Valvoline?

The same 360 that I'm talking about in my head gasket thread ran strictly on full synthetic its whole life as soon as the initial break-in was done, and so far what I've seen is the bore wear is almost non-existent after 25,000 miles and cranking compression was even across all cylinders when I checked last summer. Haven't gotten the bottom end apart yet but I'm guessing it will look the same. Initially I ran Valvoline full synthetic (VR1 with extra Zinc) then a few years ago I switched to Brad Penn; I've always used 20W-50 or a blend of that and 10W-30 in the winter because my engine has wide bearing clearances and the oil pressure gets a little low at idle when the oil is up to full temp if I just run a 10W-30.

I've never tried Castrol synthetic but I did once run their conventional in my '93 Jeep Cherokee with the 4.0L I-6; it was a big mistake, before I reached 3000 miles it was blowing blue smoke out the tailpipe and pinging like a b!tch above 3000 RPM. Changed the oil back to the tried-and-true Valvoline full synthetic and added some Engine Restore in a can (blue stuff with the tiny Copper/Silver/Lead particles), the smoke and pinging stopped and I got all my power and gas mileage back. I have no interest in trying Castrol brand again unless some car I have calls for it specifically.