% Stat vs Atk

Hello, I'm sure this has been asked before but I'm not exactly sure how the formulas end out. I tried running them but the results I got didn't even end up close to a reasonable number. I'm trying to figure out whether flat attack or additional %stat will yield more theoretical damage, given a high percentage already obtained.

Let's say I have 600% primary stat and oh, 500 att, and I could either add an additional 36% primary stat OR flat 15att and 50 all stat, but not both of those things. Which one of these would result in higher damage?

just multiply them by each other for an easy way to figuring that out, whatever gives the bigger number is better.

by them i mean your total main stat and your attack

Oh it's that simple huh? XD Thanks! :3