If you would like a place to sit and hang out in a large downpour while cooking and still be able to look around outside I would get the Hex. If that's not as important to you the stock tarp will work, but if the weather turns bad you will have to close it up (Tighter to the hammock) to stay reliably dry. Both work just fine. I used the stock tarp for quite a while here in the PNW and never got wet.
I have moved onto a even larger tarp most of the time now days.
I prefer being able to have a friend hang out and chat when in storms and my tarp is big enough that if I had to go to ground I could easily fit under it without issues.