Roth vs traditional always comes down to marginal rate now vs (expected) marginal rate in retirement. One twist is that now, with the 199a pass through deduction on qualified business income, traditional solo 401(k) contributions reduce the deduction while Roth contributions do not. What this does is reduce the marginal tax savings of a traditional solo 401(k) contribution by 20% making Roth more attractive relative to how the number used to work out. Traditional may still be the way to go, but Roth is more likely to be the way to go than it used to be.
At your income level you're probably in the 22% bracket, but maybe close the 24% bracket depending on your other deductions (like whether your husband's 401(k) contributions are traditional or Roth). Contributing to traditional solo 401(k) will save you 17.6% or 19.2% respectively. Even a moderately mustachian budget in retirement that all comes from tax deferred (as opposed to some coming from taxable or Roth) would have tax rates below that meaning traditional is the way to go, and if you expect state taxes to be lower in retirement that would also favor traditional. As you can see, once the QBI deduction is factored in it's a lot closer to Roth making sense though, so if you have a low state tax rate now, making Roth contributions would be pretty close to an ok idea (not totally optimal, but reduces some future tax rate uncertainty).
