Yes, you're so right about "好叻果d你就驚佢會出去作反" and more problematic is they may not listen to you; or they pretend they listen to you and then at your back, they go back to their ways. That's what bug me.
Experienced maids:
PROS: can run the house immediately (even though it may not be the way I prefer)
CONS: can be a smart-ass and have already establish their work habits; may not listen to the way I want things to be done.
Non-experienced maids:
PROS: required lots of training.
CONS: start fresh as a white piece of paper and I can mould her the way I like.