[Iam Canadian]

Gameplay-wise, Spaz is definitely my favourite. I can't live without that double-jump now. Plus, the side-kick has its uses.
Personality-wise, it's hard to tell, as Lori doesn't really have a defined character as Jazz and (to an extent) Spaz have. The only one we know much about is Jazz. All we know about Spaz is he apparently can be either hyperactive or a lazy bum, depending on the point on the timeline. About Lori we know very little.