Definitely the saucy expression and the obnoxious personality. Any Chi who enters the ring and is like "hello I'm here!!!!" is a winner.
For example: this
little guy is not very typey, therefore judges would mark him down for that. But his personality is INSANE and he has such ring presence it's crazy. I've seen him in the act a few times and he just thinks the world of himself and struts his stuff, even with a hopeless handler he still wins because he is a real show man.
little girl wins for her looks. She's a beautiful girl and looks just like a Chihuahua should. She is also very feminine and judges love that.
If there was a big personalitied Chihuahua and a typey Chihuahua standing side by side and the judge had to pick out of those for BOB, the judge would choose the typey one because at the end of the day it's more about looks than personality but the judge would definitely have a tough time picking it.
Which is why I think a Chihuahua is such a hard dog to show, they need the beauty AND the brains LOL
In Australia, the Chihuahua should have big, dark eyes, large ears, short legs, a stocky body and a giant round head with a 90 degree angle from their snout to their head.