Don't contribute to Roth IRA?

I have a 457 plan through work, which has a Roth option. usually I save up every paycheck so I can lump sum my Roth on han 1st. I recently asked in this sub about timing questions, and it was suggested to not save up then dump in my IRA, but instead just invest in the 457 with what I would save for the IRA, for longer time in the market. if I do this, then I can only contribute (DCA) to either the IRA or the 457, as contributing to both would be too much for me. I don't see why contributing to only the 457 would be bad, as it has a Roth option, and has higher limits if I want to contribute more after a raise or something. I also have a 401(a) through work, so the 457 / IRA isn't my only investment. thank you