For soloing raids, it is much better to have mons with the right type than to have overall powerhouses like Groudon or Kyogre. For example, Gengar with only a max cp of 2619 is far more useful than Kyogre or Groudon (both a max cp of 4074) in soloing Alakazam raids.
That being said, for your question about which Groudon you should power up, wait till the 15th of january. You could always catch a better one, right?.
For soloing tier 3 raids I see use for Groudon as an anker in Sludge Bomb Gengar raids, in Omastar raids (Groudon with Solarbeam has the highest TDO against Omastar) and in soloing ninetales.
For Kyogre, I think there is less use with only a role for it in soloing Ninetales.
