My 401k has better funds than I could ever get in my IRA. Yes, many 401k's have terrible fund choices but by no means do all of them fall prey to that.
Also, if you're maxing out both your IRA and 401k limits, even if you have a lousy 401k, you now have tax-advantaged dollars that you can roll over to Vanguard or Fidelity when you change jobs.