[LittleFreak]

Advantages and Disadvantages of the JJ2 characters:

Jazz:
Uppercut: With his uppercut Jazz can jump higher then normally, and destroy enemies and destructable blocks above him. However, it's not as handy as Spaz' double jump.
Heli-Ears: Jazz's Helicopter ears are very useful in some situations, especially if you want to jump very far.

Spaz:
Double Jump: My favourite of all special moves. Spaz can directly change his position in mid air, that way he can jump high AND far. A combination of Jazz' special moves, but without the ability to destroy blocks above you.
Sidekick: Spaz can't kick blocks that are above him like Jazz can do, but he can easily destroy horizontal blocks and also kill enemies with this move.

Lori:
Heli-Ears: Lori has the same ability as Jazz to use her ears for far jumps.
Spin Attack: It's similiar to Spaz' sidekick, but a lot more useful. Very good for killing enemies, aswell as kicking blocks.
Ducking: If Lori shoots a Hatter while she's ducking she gets hit by the Hatter's shoot, which doesn't happen to Jazz and Spaz.

OVERALL:
Spaz is my favourite, because he can do everything what Lori and Jazz can do, except kick blocks above him. If you need to get to a higher place with Lori you need to use a special trick, which is not all that easy to perform which makes her kinda useless in most levels. Flying enemies above you can also be killt with shooting up, you needn't uppercut for that, so Spaz is the best (IMO).