Sylveon won't be able to have two energy attachments every turn (Fairy and DCE), so I guess they can't win the prize trade. Sure they get a OHKO, but only after two energy attachments. If they Plea GX they are not taking a KO, meaning you'll get the chance to maybe get a OHKO for the first prizes, and even if you don't, you're still faster I guess.
I just don't like the fact that you need attacks to get the energies done (Latias Prism, Zeraora's GX attack), that's why I chose Vikavolt, but I guess Zeraora / Shuckle will work indeed and might be better / faster. But I do like to get a good turn 1 and use Rayquaza's GX attack T1 as well to start T2 with 10 cards (except for Judge from opponent or something). I'll have to test then in that Standard format.
For now, I'm focused on my next big tournaments (which would be Frankfurt Regionals last weekend September and SPE Lille early November). There I might decide to pick Rayquaza / Vikavolt.
The next four months we'll have to see how the meta will change. Relevant for me will be how good Buzzwole (normal and GX) will or won't be in like 4 months, given the weakness of Zeraora / low HP Pokemon on the bench (Shuckle getting 2HKO Jet punched on the bench while maybe getting serious damage / OHKO on Zeraora GX in active).
Join the dark side Luke
. Rayquaza will still be relevant in the SM-on format if not better than in the current standard format. While most decks need to take care not to overextent this deck does the exact opposite. Not sure that Sylveon GX is the most ideal and versatile direct counter to this deck. I much prefer Mighty Mouse from Forbidden Light since it can be teched into any deck that runs Double Colorless Energy and Tapu Koko.
I would not underestimate Malamar decks at all. With the release of Tapu Lele non-Gx the deck will have a lot of tricks at its disposal. You just need to find the ideal balance between Pokémon GX and Pokémon non-GX in this deck. I also would not count out Garbodor at all. The new SM-on format favours him a lot.
I'm not trying to treat Sylveon GX like it's in a vacuum. Just like how Rayquaza GX leans on Shuckle and Zeraora GX to get the job done, Sylveon GX would similarly need other Pokemon to work with it in order to see success, such as Gardevoir GX for energy acceleration and tech cards for more efficient prize trades.
I'm simply giving an analysis of how Rayquaza GX sets up and one of the best ways to keep it under control. The fact of the matter is by the end of turn 2 or 3, Rayquaza GX will usually have 2 to 3 Ray with 3 energy on them a piece, and 1 energy on the Zeraora GX for a total of 7 to 10 energy on the field. Usually I will have Wishful Baton attached to at least one Rayquaza, so taking a KO doesn't slow down their damage momentum in the slightest unless you Magical Ribboned for a Field Blower in advance. The turn that Rayquaza GX uses Zeraora's GX attack is the turn that you have to respond with Plea GX.
Plea GX removes 2 Rayquaza GX and 6 energy from the field, leaving Rayquaza GX with only 4 energy on the field (120 damage) assuming there were 3, and only 1 energy on the Zeraora GX assuming there were 2, which is not enough to even counter OHKO a Sylveon GX on the following turn, and in the event that Ray only managed to get 2 of them set up, you have completely deleted all OHKO threats from the field as Zeraora GX cannot OHKO Sylveon even with a choice band. Ray GX would need to find a way to get at least 90 more damage on the field, assuming there is even one left, which is 3 more energy, and even if they do, the point is that you would have another Fairy Pokemon set up, such as Gardevoir GX or Dedenne, and since Rayquaza GX depends on Zeraora's GX attack to gain early momentum, you interupt that momentum with Plea GX and force them to recharge energy by attacking with Shuckle or Latias Prism Star, buying you more turns to get your own set up in place.
The point is that you have to control the deck's momentum, and when you're looking at 3 Rayquaza GX fully loaded with 3 energy a piece, taking a single KO with Dedenne or any Pokemon isn't going to do that for you. Sylveon GX is one of the few Pokemon that are capable of resetting or at least slowing down the deck's overall momentum so that when you take a KO you still have time to prepare for the next. I don't really think I'm talking out of my rear end on this one since I'm talking about this from playtesting experience, not just theorycrafting. Sylveon GX forces Rayquaza GX into an awkward situation, and from there you can find your KOs through other methods.
I still have yet to see a Magical Swap Lele actually make a game changing impact yet in any of the decks I've tested. Not in Malamar decks, and not a fairy one played in Gardy either to get it set up with Secret Spring. My issue with Magical Swap Lele strategy is that you are not removing OHKO threats from the field during the time you are setting up the damage on the field. Whether this damage is coming from Koko, Alolan Ninetales GX (Fairy), Black Ray GX, or any other form of spread, you are always going to need at least a minimum of 2 turns in order to take the KOs that you need, and during those 2 turns you are not removing any threats from the field or stopping your opponent from executing their strategy. UNGX could very easily spread 360 damage across the full field with its GX attack vs Ray and then Magical Swap to take 2 Rayquaza GX KOs, which is how the play sort of works in my mind, but considering that the deck runs Shuckle and Ray GX will likely have one in play on a full bench, you will end up KOing the Shuckle for 1 prize, and then your damage total drops to 300, which is no longer enough to take any more than 1 KO.
Alternatively, regular Necrozma GX could still get the job done since the average Rayquaza GX board has 4 GX Pokemon on it at a time (Zeraora, 2 Ray, 1 Lele, or Zeraora and 3 Ray), so you can place 400 damage on GX Pokemon and then spread it around. I'm just not sure how realistic the entire set up is since getting an entire Malamar system in place with Dawn Wings Necrozma GX, either Switch or Altar of the Moone, two Malamars, and the Lele is, in my experience, simply a lot more inconsistent than the way Rayquaza sets up.
I don't want to count out Malamar from the picture, but I definitely am not certain how Malamar can consistently win against Ray with the way the deck inherently sets up and with how many individual pieces it needs to get going, and I would totally be okay with being proven wrong by a deck list and performance that shows it performing as intended.
