IMO, as a UPS pilot:
This was a once-a-century event that was exacerbated by the government response to it. Not sure I'd throw away five years at a legacy (that's gotta put you what, 75-80% total seniority?) to start over at the bottom of the UPS or FDX list but there's little downside in applying, interviewing if selected, then making a hard choice if offered a class.
Unlike the early 2000s, the three pax legacies have massive retirements over the next few years which hopefully will help reduce the numbers and length of any furlough.
Caveat emptor, YMMV, etc.