Neymar Doesn't Hesitate to Hack
One thing that Neymar does that Messi doesn't is aggressively go after other players and foul them.
Messi is pretty much calm and cool the majority of the time, even when he gets hacked. But Neymar, perhaps being a bit younger, doesn't hesitate when it comes to going after defenders and hacking them when he's fouled or his teamamtes are.
There's no reason for it though. Neymar should leave this type of revenge tackling to his teammates. When he arrives at Barcelona, he should let Pique or Puyol tackle hard and stick up for him when needed. There's no reason Neymar should risk getting injured or a red card by wilding charging at someone.
There's a lot of tackles and falling down in the video below, but watch Neymar come charging at the defender at about the 11 second mark - he's lucky he didn't get hurt himself. I don't think Barcelona's going to want Neymar trying to rough up other players or tackling like this. They don't want Neymar to risk injury.