For those following on X I had something incredible happen during Necrozma raiding, I got my first ever shundo for goateeVGC and was able to get enough lunar and solar energy so I can fuse both hundos so that was a thrill. Now at 269 xl candies and enough that can be traded if over 100 km I can max one of these. Lunar for the non-shiny with the special background caught in July, and the solar for the new shiny. I'm open to suggestions which I can max out first as I may end up doing the shiny since the solar version is ranked slightly higher in the master league GBL.
First, congrats on a Shundo, those are extremely rare (only have 2 myself playing since Launch).
If you're investing for the sake of Master League alongside raiding, the primary thing to watch for is 15 ATK and 15 DEF to avoid missing Breakpoints/Bulkpoints (can elaborate but essentially a stat threshold to cause moves to do 1 more/less damage), which the Hundo obviously hits but I want to ask about both.
Dusk Mane is currently better in Master League since a lot of Dragons are popular up there. Dawn Wings is good but a lot trickier to use as a result of several things with Dark/Ghost Coverage such as Yveltal, Crunch on Zygarde, and the rare Marshadow (runs Sucker Punch as its Fast move) that can really exploit it for energy. If you're trying to get your foot in the door with Mons that pull double duty as Raiders and ML mons, I suggest Dusk Mane Hundo first for a max-out target.
Raiding wise Dawn Wings will have more mons it can hit hard thanks to a lot of Psychic Legendaries (and Ghost but the 2x weakness makes that Boss-move dependent), but it's also a lot easier to find "budget" or alternatives of close-enough power for those fights like Shadow Tyranitar, Hydreigon, Shadow Weavile, and a decent few Megas, while Dusk Mane comes up less frequently (only a few Steel-Weak Legends like 2 of the Regis, Kyurem, Xerneas, Zacian) but is harder to replace in its role (next closest being Shadow Metagross w/ Meteor Mash, then a steep drop off to normal Metagross and Metal Claw/Iron Head Dialga).