It’s depending on how the cell is used, in which flashlight. I did try several 21700 cells (LG M50, Samsung 50E, 48G, 40T, 30T, Sony VTC6A, LiShen LR2170SA, LR2170SF) on two versions of ACEBEAM EC65 (XHP35 HI and Nichia).
With sufficient cooling, I activated the Turbo again and again, until the cell voltage was too low to sustain that brightness level. And the results are:
For both EC65, the 40T was slightly better than VTC6A. And the AC 1khz IR was also smaller on a 40T.
For a XHP35 HI EC65 (high demanding), 40T provided the longest Turbo.
For a Nichia EC65 (not that high demanding), LR2170SF provided the longest Turbo. This is surprising but yet reasonable, since the characteristics of this cell are between 40T and 50E.
Since some of these cells are not that easy to find, and I cannot assure you that my samples are consistent with what you can buy, you’d better take these results as reference only.