re: Roth IRA & 401k tax strategy question

In my Roth IRA and in my 401K i'm about 50/50 Vanguard S&P 500 index/ Vanguard Small Cap stocks. From a tax perspective (when i'm getting distributions in retirement), would a more optimal strategy be to put 100% of the small cap stocks in the Roth IRA account and 100% of the S&P 500 Index $ in the 401K account (taxable). With the bet being that the small cap stocks would end up having a much higher capital gains (non-taxed in my Roth IRA) than the S&P 500 index (taxed in my 401K).