It depends, Pokeathlon stats are different for every Pokemon even those of the same name. Give me their stats and what event you want them for. Make sure to tell me if the stars are black or big stars. Stats also change with Aprijuice. Here is what you want for each Pokeathlon:
Speed: High Speed, Skill, Jump, Stamina
Power: High power, Stamina, and skill.
Skill: High skill, power, and speed
Jump: High jump, skill, power, and speed.
Stamina: High stamina, power, and Speed.
Edit: I am leaving soon so I'll just tell you how to choose the best one for the Hurdle Jump. Add the number of stars for Speed and Jump together, adding one if one of the stats is a big star stat. If you have any black stars in Speed or Jump, don't use that Pokemon. Use the Pokemon who has the greater sum of stars.