I've been in a situation where it would have been better to sleep on the ground and there was a choice.

Goat Rocks Wilderness Area in Washington. The rain/mist/clouds were blowing sideways, and the last two trees before having to cross a glacier (miles before going below treeline again) had the hammock oriented so that the mist was blowing through the ends of the tarp.

I gamely soldiered through it, hung my hammock and coped, but I'm certain I would have been more comfortable had I slept on the ground that night.