As far as I know, all 401ks charge recurring fees to the employees. Some even charge percentage fees based on your balance. This is on top of the fund fees you'd have to pay for Fidelity/Vanguard/etc funds.
Also, as far as I know, personal IRAs at places like Fidelity and Vanguard do NOT charge recurring fees.
Isn't it always better to roll over your 401k at a company you left into your own personal IRA where you have no fees, and can invest in whatever funds you want?
I'm trying to think if there are any advantages to rolling over a 401k into a new company's 401k, or leaving it in the old company's 401k account...