Hi. I don't know if this would apply to you or not, but our small biz/partnership just opened the 401k with betterment and we love it. It allows us so much more flexibility, as well as the option to max out at a much higher contribution rate than the IRA. They have a roth 401k option as well. We've been really, really pleased with their service and feel like it was a really good option for us. I learned of Betterment on the MMM site, and have been really pleased with them overall.
Vanguard is fine for my personal accounts, but I have to say that on the business side, I really like the more nimble approach, the customer service, the website features and the fact that it's just more 21st century in terms of their overall platform. This might sound odd to some, but the other thing I've really liked it getting to talk to the same person for our questions, needs, changes, whatever. They have been super responsive and I have been really impressed with them.
Hope that helps!
Terri