This is my experience with UOA's on my LS1. I have a 420rwhp@396rwtq H/C 02 LS1 SS. CNC heads, small TR224 cam, all supporting boltons, headers, intake TB, etc....
Rev limiter is 6800rpms and shifts for max power are at 6500rpms.
Out of 8 UOA's 15W-40 Mobil Delvac showed the best wear control compared to Mobil 1 10W-30 and Schaeffer 10W-30. IMO For a hard run performance application thicker is better. The same thinking is used in the marine world of engines. 40W and thicker is standard to keep the engine alive.