Originally Posted by Reno Bay
I don't know of any. The "best" (classic) breeds for dressage are traditionally Andalusians and Lipizzaners (I was reading a book and I can't remember if it said Thoroughbreds were introduced to the discipline earlier or later). Thoroughbreds and Warmbloods do well too. Warmbloods were introduced after Thoroughbreds, but they all do very well.
Someone at my barn had a Percheron/Standardbred they were doing dressage with.
The Iberians (andalusians/lipizzaners) are great in the collected work. However they generally lack the scope in paces and ability to extend their paces, to do well in competitive Dressage. We are very slowly starting to see some of the Iberian breeds being produced with scopier paces. But traditionally, they are very flat movers. Look at a video of the stallions in the Spanish Riding School. They are brilliant in the collected work, but in their normal paces, their hooves barely come off the ground.
In competitive Dressage, we want a horse with scopey paces, with suspension and some 'excitement'. This is where the warmbloods come in. They don't just "do well too" - they DOMINATE.
Thoroughbreds can do quite well, though there are not a huge amount of them that make it to the higher levels. They tend to be quite stuck through the back, and struggle with the collected work. Not all, but the majority.