One area where Gtasks shines over Keep (for now) is that a LOT of widget developers support Gtasks. Like Simple Calender and Dashclock being the more popular ones. I used to use Simple Calender but now use dashclock but both are great at showing your Gtask lists on your homescreen widgets, and Gtasks does sync with your Google account so it'll appear on all your devices with Gtasks installed. Once Keep is supported by more widget developers and has Notifications for date/time I'd consider switching just to streamline my apps a bit but for now Gtasks is great for those purposes.
PS: Once Gtasks is set as your default tasks app it will also take notes made with Google Now's "note to self" command