I've done both.
Skydiving has more kudos, and I got addicted to it when i was younger, and spent most of my student loan doing jumps every other weekend.
However, Bungy is actually more scary.
When you push yourself out a plane, it's so high up that your brain cant comprehend the fact that you are high and so isnt actually scared of dying. Even when you're falling before opening the chute, the ground always seems far enough away not to bother you, and doesnt even feel like it's coming towards you.
BUT bungy is MUCH more scary, as you're closer to the ground. When you fall, you can see the ground rushing towards you, and so you get much more a "im going to die" element.
So, bungy jumping is MUCH more scary.
But I personally think skydiving is more fun, and addictive as there's more to it.
A bungy jump is just a fall and a bounce
A skydive (once your experienced) is LOADS more fun.. even at the start its fun, as you have to think about position, untangling ropes as your falling, aiming yourself towards the target in the winds, landing, etc etc.
Bungy is a quick - no brainer - rush
Skydive is fun and you have lots to do/think about.
So skydiving EVERY time.