After having a few matches, I've learned that Chesnaught without Roar has a tougher time checking Aegislash (still very much doable with Leech Seed, but more difficult if Aegislash decides to continue to SD up), and while Gengar without Dazzling Gleam/Psychic/Sludge Wave can't actually do anything to Chesnaught, if it gets a sub up, well, Chesnaught (again, w/o Roar) can't do much back.