Most high performance conversion companies (now called tuners) use Redline. Mostly 10W-30 for cars up to 800 HP. I do think Redline from everything I read is the best stuff out there; especially in lower viscosities. I am going to say their 20W-50 is around near equal to Mobil-1 V-Twin.
If I wasn't using V-Twin my next consideration would be Redline.
Mobil-1 V-Twin has high ester content that prevents condensation dispersal and facilitates better burn-off easier.