I find the bag liner to be a very versatile piece of gear. You can wear it like a kilt in camp or laundromat. I hammock camp and use a Borah gear tarp as a rain fly. On warm nights my tarp, pad and liner will make a nice alternative when I want to sleep out. All being said, I also have a pair of REI Co-Op merino wool tights that aren't as versatile....I mean they are just base layer leg coverings....but they are comfy and can be slept in, hiked in, whatever.

TL;DR Just take both on a shakedown hike. Or take them both to Springer. From what I gather people are dropping all kinds of gear in the first few days anyway. Its normal.