It's Ally, and just as with the banking, they have great customer service and fun quirks about them.
It's easier to transfer money without having to leave the site.
Since I use Ally banking, it makes it easy to see all of my accounts in one dashboard.
It doesn't have an investment calculator, to determine how many shares of stocks can be purchased with a set amount, on the stock buying page.
It's not much different over other investment providers and has the same basic layout and functionality.
Transferring money, even from an Ally bank account, is difficult to find.