In my garden, slugs tend to be the destroyers of seedlings, but the pill bugs will go after damaged parts of the stressed plants. I had pill bugs swarming over a poor nearly eaten squash plant a couple weeks ago, and initially thought they were the culprits. Once I shoed them off I saw the slime trails though. I think once plants get stressed enough it triggers the pill bugs to treat their wounds like decaying matter. I do a slug walk through the garden at night a couple times a week, and it is pretty crazy the number of slugs that exist in a small, 25'x25' plot, and most of them are very well hidden in the daylight.
Pill bugs do go crazy over fruit if it gets even slightly bruised, though. Many a fallen plum has been made less appealing looking by their chomping out of the bruised bits.