Why Personal Capital and Mint? Is there something Personal Capital sucks at?
(I'm asking because I currently use Mint and might be willing to switch, but I would probably not be interested in using both at the same time.)
Mint is great for setting and keeping a budget or at least I've found it to be so. Since finding MMM and downloading Mint to my smartphone, I've slowly lowered my budget every month and it's been the perfect companion app for that. I'm quick to recategorize things when necessary in Mint, including Hiding From Budgets and Trends my 401k contributions which invariably show up as uncategorized spending.
With Personal Capital's interface, which is incredibly slick in my view, I actually enjoy monitoring my investments and tracking my net worth in ways that Mint just cannot do.
You may be able to do it all in Personal Capital, but since I use both as described above and it works for me, I can't speak to PC's budget tracking abilities. Since they're both free, and checking my accounts is an enjoyable aspect of the MMM lifestyle for me (I probably check each once a day on average), I really don't mind using two different apps.