Standardbreds exspecial right off the track without any training tend to be easy to handle of the ground, but a handful in the saddle. But once they learn the difference between the saddle and the harness they are great. Not really good beginner horses though, without training.
I own and retrained a 16hh bay roan mare Mooney (everyone swears she is a quarter horse), and looking at a 17hh pure black gelding.
