Search a Pokémon to see the best IVs per league (Great, Ultra, Master), ranked by stat product. In Great and Ultra League, a lower Attack IV often ranks higher because of the CP cap.
In PvP (GBL), within the league CP cap (Great 1500, Ultra 2500), a higher stat product (Attack × Defense × HP) is stronger. With a CP cap, a lower Attack base lets the Pokémon reach a higher level, gaining Defense and HP, so it ranks higher. Master League has no cap, so 15/15/15 is always #1.