I prefer the larger size yorkie, around 9-10 lbs is perfect. My previous yorkies were all 7 lbs and under, and I was always a nervous wreck with them. Constantly hovering over them, worrying they'd get hurt, stepped on, etc.
I'm much more relaxed now with Snickers and Baxter, 9 lbs and 12 lbs.
They have all the beauty and attitude of the breed, but in a sturdier package.