Picking the best Discipline?

I have lots of colts and fillies at the moment and I'm struggling to pick out disciplines to focus each of them on. What are the best skills for each discipline?

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Personally I always pick the discipline I want and then get horses to match, but if you already ahve horses and are alright with different disciplines horses will do better in shows if you pick the discipline which they exhibt the highest stats for, so a horse that has the most stats in Speed and Agility would do best in Show Jumping, while a horse with really high strength would probably excel in Driving.