i'd put it as jiggs > peach. or possibly jiggs = peach. but...
peach can't really get past bair spam. and what's even worse than bair spam for peach is if the puff waits till she tries to set up a fair, and either bairs her first, or bairs her just after she misses (better), neither of which is terribly hard with puff's great air mobility. she can pull turnips, but she has to hit with them too, and that's pretty hard with, again, air mobility, and with jiggs being able to stop turnips with all of her aerials (not that you'd ever do that with dair, but afaik it would work).
her other aerials compete with puff's other aerials, maybe, but not with puff's bair.
you're right, jiggs can't easily gimp her, but it's not like she has to. peach can't either. same with rest, it's hard for jiggs to rest peach, but she doesn't need anything that powerful to even the playing field. the matchup is mostly a spacing war, or more specifically, peach's fair vs. jigglypuff's bair. and one of those goes notably farther than the other. *points to hungrybox's signature...if he hasn't changed it yet*
but yeah, peach does have turnips and fair and lives longer than jiggs while being able to escape most of her combos...so even is arguable. but i'd say jiggs > peach.