I guess I'm in the minority. My friends all said all boys until I tell them this and they see where I'm coming from:
It's not a CERTAINTY but its MUCH LIKELIER your daughter(s) will be more respectful. When you're old, they will call you multiple times a week and visit you on the weekends compared to your son who will call be like "Hi...yeah...your good? Ok...give the phone to mom".
Likelier your son will have a bad crowd of friends than your daughters, likelier they will be potheads, alcoholics, commit crimes than girls.
The problem with many guys not wanting girls and assuming they will turn into sluts is the past few generations the men pass the daughter down to the mom and expect her to take to her to the movies, ballet, shopping, etc. There are certain things a man has to do. If you can raise her right (and even a boy) then there shouldn't be a problem.
But yeah my main concern with having daughters is other boys lol.