Not sure if you’re on the wind up now.
Sterling has never been as good at LW as Sane and likely never will be. As for skill, trickery and pace, Sane is the full package, far more so than Sterling who relies heavily on speed and has barely beaten a full back all season on the left.
I think it centres on how we're defining 'LW'. My point is that in Pep's system with inverted wingers he prefers Sterling. Maybe you are calling that an inside forward? Under this system Sane had essentially been reduced to being used tactically: impact sub for counter attacks, occasional starts against teams that actually attack us like Liverpool, and starting in lower profile games.
If you'd argue he's a better player than Raheem in our usual setup then I'd point you to their stats for 17/18 and 18/19. Raheem comfortably scored and set up more goals. Would you start Sane over Sterling?