Better Groudon?

Maxing out higher is irrelevant, 5 CP doesn't mean anything.

If you want a future-proof Groudon - i.e. you're worried that the one that has 13 attack IV won't be able to hit a breakpoint - then max out the one with 15 attack.

A difference of 3 defence and 1 stamina IV is not significant, especially if compared to the potential difference of hitting an otherwise unreachable breakpoint.

Regardless if you're using a maxed out Groudon to clear a raid that it is useful in, you're going to clear it with ease even if you are missing out on 1 damage from your quick move so I wouldn't worry about it too much.

I would go with the 96 IV one, because Groudon's highest base stat by far is attack. So, discounting his attack a couple points from absolute maximum is unlikely to make a practical difference. Improving his survive-ability might let you get off one more charge move in rare cases. However, in most cases, none of this will make any difference whatsoever in the outcome of a battle. You'll have better bragging rights for IV percentage, and save some dust and candy for other things.

BTW, I do get the breakpoint thing, but the exact threshold you need to hit varies with the raid boss, and it is going to much more important as to how many trainers join the raid, and what other mon you put on your team. If 20 or thirty points of damage makes or breaks a raid, you're playing on the pretty extreme edge, and in most situations, it won't be that much, if anything.

You weren't excited once you found out it was 13 attack? .-.