Both are fundamentally the same. Has anyone defending trolls here actually conversed with one? Someone who lies and acts like a dick simply to cause a negative reaction from you for their own enjoyment by definition is bullying, in this case, cyberbullying.
Now here's the kicker: are bullies always wrong? Do some people deserve to be bullied? The answer is almost universally no, but I like to take a karmic approach: those who bully or troll deserve the same. Such behaviour should be rewarded in an education in empathy for the victims. So next time you see a troll, or a cyberbully, don't feed them, don't get mad. Simply troll them back.
Act like the biggest idiotic version of them towards them. When they insult your sexuality or threaten you sexually, simply reverse it back on them, my favourites being when they threaten you sexually, and since they are always homophobic men, tell them you don't swing that way and that homosexuality is just fine. If they call you gay, ask them what their problem with this is. Make them MAD, not yourself.
Show the homophobic, xenophobic, ignorant brats just how annoying they are. Don't get mad. They're not even brave enough to try to pick on people who can even fight back, let alone someone their own size.
TLDR; cyberbullying=trolling. Some people are dickish enough to deserve the practice.