I would not introduce the complication of a second taxable account to save $153 over a year or two. That's probably before taxes, and your taxes on that $153 are probably $20 or $25, so you're only talking about $125 or $130. Over one year that's about $10 a month, over two years about $5 a month. For me it would be easier to skip a Starbucks or a bag of Doritos or a fast food meal.
To get that, you need to open a Vanguard account, set up your transfer accounts, transfer money around, learn a new website, and deal with another tax form at tax time once or twice at least.
I respect the argument about security and account bonuses, but for me I don't see those as a significant issue. It is very rare to begin with, I keep good security practices and there is SIPC insurance against fraud and theft. As for account bonuses, the ones I've seen are usually for new customers and/or new money, and those are similarly not worth it for the hassle factor vs. financial benefit for me.
Also, CD and money market rates bounce around from week to week, day to day, and hour to hour. It's possible that they day you checked, Vanguard was ahead by a bit. If you check at a different time, Schwab may win.
For what it's worth, within my family we have accounts at both Vanguard and Schwab. I like them both, but I don't like either of them enough to have accounts at both or bother switching from one to the other.