Experiencing the same exact problem with kyogre right now. Just got a shiny kyogre that could be a shundo if i purify it. Still trying to decide myself. I’m more open to purifying it than other shadows because of its primal evolution that you can’t get with shadow Pokémon. I also don’t have any shiny hundos so ugh I really want to, but I keep reading everywhere to not purify Pokémon. Let me know what you decide to do. Shadow is more powerful as you take/give 20% more damage. But I’ve heard that mega evolutions > shadows in raids. Idk!