If there would be a "best" one, there wouldn't be a setting for it in menu (the camera would always use that one).
The one chosen by ETTR should be optimal (in the sense of constrained optimization - you choose the slowest shutter speed, the lowest SNR you are OK with, and how many highlights you are OK with throwing away). If you find a situation where ETTR result is not optimal, report a bug and show what setting was chosen by ETTR, what you think it's best for your situation, and a side-by-side comparison that shows the difference.