My company was just sold and the new management picked Transamerica Retirement Solutions as the 401k provider with Schwab as the SDBA, which I participate in (most of my assets are in the SDBA).
Aon Hewitt was our old 401K provider; Hewitt charged $20 quarterly fee ($80 annually) for their SDBA, so the $50 Schwab fee is an improvement...
In regards to any Vanguard funds in the Hewitt SDBA, I could only buy their Admiral Index funds (for some reason the ETFs weren't allowed). The purchase fee for Admiral funds is higher than for their corresponding ETF funds, but the expense ratios are way low, so I was willing to take a small hit for that...All those funds transferred into my new Schwab SDBA.
With Schwab, however, I am allowed to buy Vanguard ETF index funds, so I am looking further into that. I also dabble in a few selected individual stocks...
see this BogleHeads link for further perusal:
Lazy portfolios - Bogleheads
and this for alternatives using Schwab funds:
Three-fund portfolio - Bogleheads