Honestly, the one who has a rigid schedule that, if disturbed, has a knock on effect to the rest of the world!!! If things don't get done here they get done late, its not a big deal!!
Am I old fashioned, I always thought au pairs were to look after your house - eg clean, make dinner etc, not for permanent childcare - thats a nanny, surely.
And what sort of interview do these mums give the au pair - they seem to know nothing about them when they start work!!!
Snobby mums who don't pay attention piss me off!