Given your location and where you are most likely to venture, I would have to concede that the liner is more likely ideal for your needs. For what I do and where I like to go, it just isn't enough. But it would be overkill here in Florida, and where you are as well.

I'll say this, though, for it being advertised as fleece, it is as sturdy as any tarp I've ever come across. I'd have no worries using it as a ground cover under a tent, or as an awning over the top. Short of pulling out a knife, you are not going to rip, tear, cut, or puncture that stuff otherwise. It also has problems with open flame, but I've yet to burn a hole through any of mine, despite sitting beside some fairly big pine and fir bonfires at elk camp. Even if you do manage to put a hole in it or tear it, the warranty covers repair/replacement.

A poncho liner is a versatile thing, and would probably suit me better here. Any other fleece material I know of is going to be less versatile by far than either the liner or the Riverswest stuff.

In an ideal world, I guess it would be best to have both?