Specifications on Rotella T6 Full Synthetic 5W-40 for older bikes?

How does this motor oil compare to normal 10W-40 with a squirt of ZDDP, and why does it seem to be a more popular choice of oil? via /r/CafeRacers https://www.reddit.com/r/CafeRacers/comments/aru38q/specifications_on_rotella_t6_full_synthetic_5w40/?utm_source=ifttt