Why am I investing in a 401(k) and not a Roth 401(k)

If I'm going to be making 3-4x what I'm currently making in 15-20 years, shouldn't I be putting my 15% into the Roth 401(k) and not the standard 401(k)

I don't see a benefit to splitting the 15% into X% 401(k) and 15-X% Roth 401(k)


Why am I investing in a 401(k) and not a Roth 401(k)