A lot of those commenting make good points, mostly regarding soundness issues, retraining issues, price and most importantly the train-ability and heart of the thoroughbred breed as a whole. That got me thinking about the many (many, many, many) thoroughbreds I've ridden in my career, and what makes them unique.
- The Thoroughbred demands your respect and confidence. This is not the type of horse you can ignore. Spooky situations can easily escalate without a calm and confident leader to take charge. He can easily become tense or nervous when things change. Even the best behaved and docile thoroughbred prefers to have your support and attention, especially in new situations and around new people. This is mainly because ...
- The Thoroughbred is a loving, social horse with tendencies towards attachment. Most thoroughbreds are incredibly happy as one-person horses. They tend to bond strongly with their riders and caretakers, often showing an incredible amount of trust in that one person. However, thoroughbreds also love to be social with other horses, and tend enjoy playing with other horses. This may end up being frustrating to the rider, as your personal relationship may get in the way of your objective training.
- The Thoroughbred is a perfectionist and a tattle tale. He is sensitive. He will demand the most accuracy his rider is capable of, both in training and riding. Any faults of the rider, a slight relaxation of the core or half inch drop in the contact, will be reflected in his way of going. While this will make his rider ultimately better and more sensitive, it can be the most frustrating thing in the world.
- The Thoroughbred finds joy and relaxation in rhythm. He can get lost in the rhythm of his own gaits. This can be used to the rider's advantage, to relax and calm the horse in tough situations. Especially if you consider...
- The Thoroughbred's mind is only working if his feet are moving.
The thoroughbred is a amazing breed, but not meant for everyone. Most days I'm happy to have my little perfectionist workaholic, but certainly there are days where he, say, tattles on me to my instructor every time my core loses an iota of stability and I want to kill him. Certainly I think that Thoroughbreds are suited to dressage, and I believe that everyone should at some point experience the nobility and drive that these animals posses. They make their riders better, and there's something to be said for that.
And for those who are wondering? Yes, absolutely get a thoroughbred for dressage. Any good horse is completely capable of getting 60% scores at 3rd Level. As for picking the "right one?" I suggest using the same criteria you would use to select any other horse for dressage. Look for a level or uphill horse with sound legs and a happy expression. Choose the horse that will make you look forward to your training, more than the horse that is fancy. Then, focus on you. Your riding is going to do a lot more to advance you to your goals than your horse.