I went thru this decision process recently. After reading, researching, and asking some members that shoot a lot of .338s, I concluded the only reason to go with a faster than 10 twist in .338 was if I wanted to focus on shooting monolithic bullets. The monolithic bullets cost substantially more than the lead core jacketed bullets. And the ideal twist rates are different enough between these two different style bullets that I couldn't identify a compromise twist rate that I felt would work well with the best of both style of bullets. It was either buy a twist rate for the monolithics, or buy the twist rate for the jacketed lead core bullets.
It became too complicated, there was the extra cost for a non-standard twist rate from Bartlein, so I finally ordered a standard 10-twist which I decided was just fine for the 300gr lead core jacketed bullets such as Berger and Sierra.