Putting a blanket over yourself in a hammock doesn't address the underside in the same way. The Snugpak Hammock Under Blanket WGTE is designed for that lower part of the suspended setup, which is the reason to compare it with a normal camp blanket.

I'd begin with compatibility. The hammock you use and the way the under blanket attaches have to work together, so this isn't an accessory I'd buy from a name alone.

The Purpose-Built Role

Hammock-under-blanket format.
Suspended use beneath the sleeper.
A component of a larger hammock sleep system.

Check the dimensions, attachment arrangement, and the manufacturer's temperature guidance for the exact version. Use that guidance together with the rest of the hammock sleeping setup.

Fit Underneath Is the Main Job

A gap, poor positioning, or an awkward attachment can change how useful an under blanket feels. Follow the supplied instructions and practice adjusting it while the hammock is occupied in the intended way.

Also consider how it interacts with your rain cover and the rest of the suspension equipment. The underside layer doesn't provide overhead shelter, and it shouldn't crowd the components that are already there.

Who I'd Compare It For

Someone who already uses a hammock and wants a more considered sleeping arrangement has a clear reason to look at this. For occasional daytime lounging, the additional piece may be more equipment than you need.

I'd choose it when the documented fit and role match the hammock I own. If most nights are spent on the ground, a pad is the more relevant comparison. The under blanket earns its place by solving a specific suspended-sleeping problem, not by being another general-purpose blanket in the camp box.