I obviously only have boys - so does my sister - but I can tell you for a FACT that my teenage boy is a TERROR sometimes, and sometimes the sweetest thing ever. (He was a challenge to raise too, but he has autism so not sure if that is a fair comparison.) DS2 is quiet, loving, and calm most of the time, but he is very clingy. My sister's boys are like little tornadoes and always have been, wreaking destruction and mischief everywhere they go! They have bright red hair and are close in age, so I like to call them Fred and George Weasley from the Harry Potter books - that's what they are like. My SIL's three boys are also little tornadoes and her girl was always sweet and calm - until she hit teenagerhood a year or so ago, now she is rude, annoying and vindictive (can't wait til she grows out of that, OMG)
My mother had two girls and a boy, and she says that girls are easy when they are younger and harder when they are older, and boys are vice versa. That being said, she says she really appreciates her girls because we are much closer as adults.
So, I guess if there is something to it, you pay for it now or later! :)