Should I lower my post-tax or pre-tax contributions to my 401k? (opens in new tab)

I am currently contributing 15% post-tax (Roth) and 15% pre-tax (traditional) of my pay to my 401k. My company contributes a 4% base amount and matches up to 6% (for a total of 10% if you contribute 6%). So I am already above the amount they match. I am in the situation where I would like a little more spending money, so I am considering lowering one of my contribution amounts to 10%. Would it be better to lower my pre-tax contributions or my post-tax contributions? What are the pros and cons...