I would offer the following tidbit, that probably is already obvious, but then again, perhaps not....
As a credit union, PenFed has a primary interest in obtaining and then utilizing funds from it's members in order to make loans to other members (or those same members). Therefore, their trade in CDs is what I would consider a primary and direct interest.
Contrast that to Vanguard whose focus is Investing and Advising. Without a large market of folks needing auto loans, mortgages, and other traditional banking functions, they have no direct need for funds to loan out. Therefore they are by their very nature not primarily interested in the CD business. They provided access to CDs because people want them, not because Vanguard has a direct interest in the process to fund their other activities. Thus their offering of the brokered product, sourced from elsewhere which, IMHO, can just about never be as good as going to a 'primary' source. Any time there is a middle man, they have to take their cut, besides the fact the very nature of the brokered product is different.
When I need fuel, I go to a gas station. When I am hungry, I go to a restaurant. The fact that you *can* get some food, some times, at some gas stations, is not a compelling reason to make it a plan to buy your food there regularly, IMHO.