Primal Groudon is more viable, by a mile
First, I'll cover Primal Groudon
Primal Groudon's incredible physical bulk paired with its similarly amazing defensive typing lets it switch into dangerous Pokemon like Physical Mega Rayquaza, Zacian-Crowned, Xerneas, Kyogre, and Yveltal. It can use a variety of sets ranging from DoubleDance to defensive to support with Rock Tomb, Lava Plume, and Stealth Rock to mixed to all-out bulky physical attacker. Its typing makes it the best possible check to Zacian-Crowned, as Heat Crash and Precipice Blades are both super-effective. It also switches into Geomancy Xerneas, being immune to Thunder and resisting Moonblast and Hidden Power [Fire]. It also easily gets rid of defensive cornerstone Necrozma-Dusk Mane. However, Calyrex-Shadow is a threat that must always be considered, as its nuclear STAB Astral Barrages hit it on its average base 90 Special Defense. However, for that, there's Yveltal.
Now, on to Kyogre
In its first few generations, Kyogre was one of the top dogs (whales?) of Ubers thanks to its Scarf rain boosted Water Spouts drowning everything that didn't outspeed it, and the only thing that outsped it was fricking Deoxys-Speed and Pokemon in weather like Sand Excadrill. But it all changed when Primal Groudon attacked. The Ubers world didn't really need him that much, and he disappeared. 3 Gens after its viability plummeted, the incredibly broken and very poorly made Dynamax mechanic was created and Kyogre's access to Hidden Power Flying of all things made it one of the most popular mons in Natdex AG. Now where does that leave Scarf Kyogre? Outclassed and outdone by its Dynamax HP Flying set. Not only is it bait for Primal Groudon, letting it set up Stealth Rocks or Rock Polish, but it barely scratches Mega Rayquaza and Ferrothorn. However, one notable thing it does is keep non-scarf Calyrex-Shadow in check, thanks to Timid Kyogre outspeeding and OHKOing it. But why use Water Spout Kyogre if you can just use Dynamax HP Flying, or better, Yveltal?