
The main concerns here are:
- taxes - 401k contributions defer taxes (or prepay for a Roth account), and there’s only so much tax-advantaged space available
- investment options - 401k plans have limited fund selection, but many are good enough
If you’re planning to invest 5% regardless, choose the account that gives you the best tax advantages that matches your investment plan. For most, that’ll be the 401k in an S&P 500 or total US stock market fund. If the fees aren’t too bad, I’d absolutely go with the 401k.
If you’re in the 12% or below bracket, I recommend Roth if it’s available. If you’re above, deferring taxes is probably the better plan. If your funds are super expensive (say, >0.5% fees for an index fund), you might be better off in a taxable account.
That’s subject to plan rules.
If you pay the same effective tax rate now vs retirement, Roth and tax-deferred are equivalent. The benefit of Roth is that it gives you flexibility in retirement, so you can choose how much taxes you pay in retirement instead of whatever you happen to withdraw from your tax-deferred accounts.
So a Roth contribution isn’t an automatic slam-dunk, it really depends on OP’s tax bracket now vs retirement. If OP is in the 12% or lower tax bracket, I highly recommend a Roth contribution, but if they’re above it, I recommend taking the deduction. I’m a little below the top of the 12% bracket, so I actually convert my old pre-tax accounts to Roth up to the top of the 12% bracket since that’s a pretty good tax rate to lock in.