Which groudon

1

Go with 1. You can always get more rare candies but you can't improve on IVs until Groudon comes back, and who knows how long that'll be, if it will even happen at all.

Groudon with Solar Beam is still usable against Kyogre (mainly against Thunder), and with Mud Slap + Earthquake it's going to be the best ground type attacker for a long time if not permanently, unless better moves get added but not given to Groudon.

I too encourage you to invest in #1:

- Mud shot is a solid fast attack for its short cool down and high energy gain which is preferable for charging either of it's usable one-bar charge moves.

- And like androgynous mentioned it is versatile for having access to solar beam as well as its STAB earthquake.

- Investing in legendaries is more of a commitment, as you know, since their walking distance requires 4x as much distance as many of the non-legendary options, and I think if you were to eventually max it out, you would be happier with a 91% that has a higher likelihood of achieving break points than a 76%

- kyogre does outclass gyarados, but I think the gap between groudon and rhydon is greater than kyogre and gyarados because of their the difference between groudon's and rhydon's movepools as well as the fact that the difference in attack stats between the two aforementioned ground types is greater than the difference between the two water types.

- rayquaza as a flying option is solid, but we do not know when it will be released AND flying has less coverage compared to ground (flying covers fighting, grass/bug VS ground covers electric, poison, rock, steel, and fire)