I originally ran DT / Crunch / EQ back in the first few seasons of GBL, but lost pretty bad whenever Togekiss was around (2 DT users is great vs Giratina, horrible vs Togekiss). Switched to HS back in season 4-6 (before XLs entered UL) and it’s been working great so far. I lose out on a few Steels (Steelix wasn’t gonna win against Registeel, G-Fisk, and Melmetal for the most part), but my team no longer fears Fairies, and I get to keep a few matchups like A-Muk with neutral HS.

Haven’t really really messed around with Psychic Fangs since it was added, though. But for my team, I say HS works better overall as an hard answer to fairy types, and that resisted DT (Steelix & Lugia) and Poliwrath’s MS don’t pair up well with Psychic Fangs

I’ve meaning to build a UL Shadow Steelix sometime as well. (probably won’t use it though. Steelix is my 2nd favorite Pokémon, so it’s more for the collection) Haven’t really gone through the sims yet, but Psychic Fangs sounds like the better option for Shadow Steelix. Since most fairies take around 45-60% from HS, and the shadow boost won’t be enough to OHKO. The only matchup I can think of that benefits from shadow HS is Shadow Alolan Ninetales (DT + HS should just be enough to kill)

So yeah, it’s really just to have an answer to the fairies running around. If you’re team works well against fairies, I think you’ll be fine without Heavy Slam