Okay: Childbirth is by far worse. Yes, the women's muscle make up and nervous system was made to have children, but that doesn't mean the pain is any less. Women may be built to have children, but they can only barely handle it.
"Giving birth is like taking your lower lip and stretching it over your head". ...Carol Burnett Face it, if men had to give birth, humans wouldn't exist.
I honestly think that getting kicked in the balls hurts more then giving birth would. Like. The testis are tender sensitive balls.. They're a sperm factory. Imagine getting sacked and those little defencless balls get smushed against you. This happens 15-20 times. It starts to take long term damage. Also if you get kicked hard enough it can make even the manliest of men cry like baby's. There for balls would hurt the most. As well it doesn't only last a while. It can last up to hours. From my experiences :')
I'm not a woman, so I don't know what it would feel like, but I would say childbirth. I've gotten hit in the balls before... Hard, wasn't pleasant. Have to be a masochist to enjoy something like that. But from what I've heard, childbirth has got to be more agonizing. A kick in the nuts is swift, childbirth can take hours.
Some instances woman don't even get an epidural. There's no time. Happened to my sister. My nephew wanted out. And boy did he want out!