The Chojubai quince are very beautiful trees. Their flowers are in perfect harmony with the size of their leaves. They are a perfect species for planting on rocks due to their low branching habits and ability to keep a small form. I think Junipers are the best because of their small needle size - making them believeable bonsai specimens no matter what size they are. They're have much better proportions than other species.
Junipers are also suitable for many styles.
I think this makes them one of the ultimate bonsai species. Plus, it does better in south and central Texas than a lot of the traditonal leafy trees. Scale leaf junipers are just the perfect species for scale in bonsai as they can be used for thimble sized bonsai up to the big ones. You just never have a problem making them look believable. As a bonus they produce an aged bark quickly.