13A/15D/15S vs 15A/15D/10S
Which is the better investment?
edit: For Raikou
Answers
How about writing 96% Raikou vs. 89% Raikou? That makes the question clearer.
If it's for PvP, the lower attack might actually get you one more half level of powering up in the Ultra League. I have a research breakthrough one with 15 Stamina, 15 defense, and 11 attack, CP 1456, which would power up one half level to 1505. Lose a point of attack and it powers up to just under 1500. Plus, high attack isn't everything in PvP, tankiness is more valuable, unlike in raids.
What he wrote provides significantly more information. As you point out yourself later in your response, the distribution of IVs is oftentimes more important than total amount of IVs.
A lot of players worry about 15 atk IV to make all possible breakpoints.
A breakpoint calculator is a good reference for this question. https://pokemongo.gamepress.gg/breakpoint-calculator#/
Against Kyogre (no friendship bonus, no weather) Raikou' Thunder Shock with 13 atk IV does hit the final possible breakpoint at level 39.5. With any friendship, that breakpoint will drop lower.
Might consider checking other possible raid bosses if you are worried.
Okay, "PVP" is relevant information that was omitted. You can't control or predict the opponent's defense for breakpoints in PVP like you can in raids. A small difference in HP might be worth that little extra attack. Although, Thunder Shock has rather low damage either way and mainly benefits from high energy generation.
The question I would need answered is how well are you able to Dodge in Raids and Gym Battles? If you are able to dodge easily, then the 15 Attack Raikou is better because you're doing more damage overall.
If you are more likely to just tank things (ie: no dodging, only attacking), then the Stamina 15 is better as it will potentially allow you to get 1 more attack off (potentially even 1 more Charged Move, if you have Wild Charge), upping the damage potentially enough to offset the lower Attack.
For PvE: Don't invest, Raikou isn't necessary right now. 15/15/10 would be the safer option as it will always be able to hit all possible breakpoints.
For PvP: 13/15/15 has a better stat product for both ultra and master leagues. Master league meta is so narrow though that you should really make sure that a 13 atk Raikou can hit all relevant breakpoints against 15 def opponents if you want it for that.
15-15-10 no contest...irrelevant of the theory
Using the CP calc for this specific case...
They both go over 2500CP at level 26...25.5 is under 2500 - so the lower attack can't make up the breakpoints possible differences.
The difference in health is 3hp.
So, 15 15 10...unless you think 3hp will make all the difference
Sure, in theory the lower attack could make a difference...but that theory is irrelevant in this specific example.