Even worse than the iPhone prints are the smears left from the gesture locks on Android. You can see the whole thing quite clearly. I've been able to unlock several people's phones just by tracing the smear left on their screen. There's no ordering problem either.
I found it easier to pick up visually as well, and thus more difficult to hide from anyone who may be trying to see it.
On the other hand it's really hard to describe your gesture to someone if you're lending them your phone, unlike a PIN which is easy to relay verbally; you really need to demonstrate the gesture.
