There are benefits...younger dogs recover from both the anesthisia and the surgery itself quicker, for one. Also, the risk of mammary cancer at a later stage in life is reduced greatly if females are spayed before their 1st heat. Also, the surgery is less "invasive" because there is less fat tissue to work around during the surgery.
I also however understand that it is scary to think about an adult Yorkie having to have surgery, much less a baby!
I think most importantly, you just need to make sure that your vet is completely comfortable and experienced with performing an early spay and that YOU are comfortable with your vet.
