The silky terrier club of america has a good comparison with pics between silky, yorkie and aussie.
Silky Terrier Club of America
You may think they look alike, but
good representatives of each breed are actually very different. Where the confusion comes in is that there are so many byb producing poor representatives of the breeds or even half-breeds like mine (who I love dearly and is half yorkie, half silky) and this blurs the lines and makes it more difficult to distinguish.