Here's a test...feel your yorkie's fur. Does it feel like soft cotton candy, or like smooth silk?
I know this is a booty pic
but look at their hair side by side:
Emma, on the left, has a cotton coat, which has softer, more feathery hair. It mats easily, and needs daily brushing. She is SO soft, no matter what the length of her hair. Milli, on the right, has a silk coat. It lays down better, is shiny, and feels smoother to the touch.
Sorry again for showing you their rear ends, but this really shows their hair types well next to each other!