Spaz's sidekick is not controllable. If the momentum of your kick stops 1/2 tile away from an enemy, you're toast (unless you got more than 1 heart). Lori's kick is faster and shorter and she is invincible against enemies (but not enemy projectile/missile attacks) so you can kick for as long as you want until you clear the area and can safely stop. She can also kill bosses using only her sidekick without getting hurt (she plows through bosses unlike Spaz who is stopped by them). Lori is great but she's definitely not my favourite because of her inability in multiplayer (her sidekick is useless against guns) and because she's a newbie compared to Jazz.
