There are a reason why I love men, and that's why they are better trolls :)
People can lie on the internet. Some might be on the other gender's account posing. Some might not have the same age bracket as they are irl. So it's really hard to say. I voted for men, though. Even if it's trolling, I see more blue users than pink that bully.
One was a mod. He just stalked me and criticised me for everything I write here and reported a lot of posts and eventually, blocked me and left this site after a few months. Second was same, but he wasn't mod. He used to criticise the admins for making me a mod and promoting me (back in 'ol days) Third one harassed me on PM, opinions comments. He threatened me to kill me. He abused my parents and my nation. He downloaded my pics and asked "rate me" questions by writing "I'm a pig ass" on it.
So, it is guys. There are a lot of girl trolls and there might be a few cyber-bullies too but I never encountered them.