It depends on your team.
Whether you need a bulky hit tanker, or a fast sweeper.
Let's look at both.
Rayquaza
This thing got a huge drop and heart break. Primarily because of the removal of Mega from Gen 8, it is doubtful whether it may get its original AG position back in USUM. While Life Orb sets can still Dynamax and even set-up, there's much disadvantage. Yveltal is already better than it by a mile because of being a better Dynamaxer.
No Delta Stream. Poor Rayquaza. This thing doesn't have much viability back as it had in USUM.
Zygarde
This thing is a freaking wall. Especially with the removal of Refresh Arceus formes from Galar, it has a ton of viability.
Defensive Zygarde-C is a premier wall in AG thanks to its ability to check the majority of physical attackers, including Primal Groudon, Ho-Oh, Necrozma-DM, and Zacian-C lacking Play Rough. Rest is important to keep Zygarde-C healthy and remove status ailments such as Toxic poison from Ho-Oh and Necrozma-DM. An anti-setup move is mandatory in order to check sweepers like Dragon Dance Necrozma-DM properly. Haze lets Zygarde-C check opposing Zygarde-C with Dragon Tail, avoid being setup fodder for special attackers like Geomancy Xerneas, and deal with Baton Pass strategies. Alternatively, Coil makes Zygarde-C more threatening offensively thanks to the Attack boosts it provides, but it makes this set setup fodder for opposing Dragon Dance Zygarde-C.
It really depends upon whether you need a bulky setter or fast Dragon-Dancer.
Dusk Mane Necrozma is much better Dragon Dance user, Coil is much better as defensive.
Sample set:
Dragon Dance
Zygarde @ Leftovers
Ability: Power Construct
EVs: 16 HP / 224 Atk / 36 Def / 232 Spe
Impish Nature
- Dragon Dance
- Thousand Arrows
- Substitute
- Dragon Tail
Defensive.
Zygarde @ Leftovers
Ability: Power Construct
EVs: 252 HP / 208 Def / 48 Spe
Impish Nature
- Thousand Arrows
- Rest
- Haze
- Glare
Thus, we can conclude that Zygarde is much better than the former, but Dragon Dance Dusk Mane seems to outpace both. Coil defensive Zygarde is much better than Dragon Dance sets.
Hope this helps!
