My take on it is (and this is JMO) that boys are harder work when they're younger. I have 2 girls, but I knew many people with boys - boys only, and a mixture of boys and girls, and also knew 5 or 6 childminders who looked after boys and girls.
Every last one without fail, said that girls were easier to look after. They occupied themselves, and were less whiny, moany, and clingy. (Don't shoot the messenger! This is what they said.) Girls would sit and draw or paint or read a book, boys wanted to be entertained and occupied, and were much more energetic and demanding. I had several friends who had a nightmare with demanding noisy clingy boys, and I was like 'awwww, my lovely girls are so sweet... And they were... honestly! Would sit there good as gold, reading and watching TV with me, or going for a nice walk.
However...When it came to the teen years, my 'slightly smug mummy of girls' stance was shot down! They turned into little beasts. There's one and a half years between them, and from 13 y.o. and 14½ y.o. they were very hard work, for about 5 years! They would accuse me and their dad of favouring the other, they started swearing, their bedrooms became untidy, and they became lazy.
They got on OK half the time, but sometimes they seemed to HATE each other. They fought physically, they shouted at each other and insulted each other, they got into big arguments with girls at school, and there was always something going on, I fell out with multiple mums because of their arguments, they both started smoking (stopped after a few months thank God.)
One got a small illegal tattoo on her thigh at 15, one got pissed on a bottle of wine at 16, and was puking all over my best rug, and they sneaked out of the upstairs bedrooms (3 or 4 times,) to go to parties that were being held some 10 minutes walk away, at someone's house where everyone was 18-22 and they were 15-16. We had to drag them back kicking and screaming from these bloody parties. They were sullen and grumpy half the time and only seemed to want us for lifts and money! And they only seemed to come home for food, and to sleep!
They were a dream as children (pre-teens,) loving, kind, funny, well-behaved, did well at school, easy to look after, helped around the house, were brilliant to travel with, and always good fun on holiday, and great to go shopping with and to take to my friends and families homes. And then they hit their teens, and were REALLY hard work. Other girls were mean bullies too, and girl bullies are far worse than boy bullies IME and IMO. It's more cruel and insidious with girls...
Right up to about 18-19 really, we had hard times with them... A good 5 years of hard work and headaches. Was a relief when they went to uni!!! They both went together. (at 18 and 19.)The older one had gap year and so they were both at uni at the same time.
They're mid to late 20s now, and are grown adults with their own home, career, and life, and are wonderful young women. Lovely, kind, lots of fun, and amazing human beings. And we're really close. Though me and DH only see them once every 2-3 weeks as they live 20 and 30 miles away. We are in touch most days via social media and whasapp though. 
So it's turned back around again. Angels to demons, and then back to Angels!
Oh btw, my friends/acquaintances who had boys seemed to have very little trouble when they hit their teens. Some of them had none. And now the boys are grown THEY are good people too, with their own life, home, and careers. So yep, upshot is, they're all pretty much hard work sometimes, and easy work/lots of fun at other times. Like all of us really. So all in all, neither one is harder than the other.
That was a bit long sorry! 