For these reasons, these are commonly referred to as "damage multipliers".I'd be reluctant to install tail light guards. From what I've seen, they are usually attached with fairly fragile mounts, often using the screws that go right through the tail light lens or tucking in near the edge.
I've absolutely destroyed my paint with branches, some of them enough to dent the sheet metal, but I've never even cracked the tail light lenses. I even got hit by a Land Rover LR4 that left a significant scuff right on the tail light lens and caved in the rear fender and door - it still didn't break.
However, the tail light guards are very likely to snag branches or focus impacts onto a small area - which increases the chance of it cracking or breaking. If you won't be in the deep brush or just want them for cosmetic reasons, I'm sure they will be fine.