One other thing to consider. If you go through your employer's HSA provider and they deduct the contributions from your paycheck, the contributions are FICA and medicare tax exempt (7.65%) in addition to your federal income tax exemption status.
Said differently, if you contribute to a plan outside your employers plan, you could be essentially paying a 7.65% fee on your initial contributions, not cool.
This is why I stick with my employer's provider (mybenefitwallet.com). I'm not impressed with them and they charge $5 a month in fees but they have VTSAX and like I said before, my 7,000 annual contribution is not taxed by FICA or medicare which saves me $535 per year in taxes which more than makes up for the $60 in fees per year.