Lol, make up your mind. Proved scientifically? What. You're talking about a video game, not a physics experiment. I've never seen you play online. Jazz does not jump higher than Spaz. Run and double jump is higher and faster than uppercut, even so, it is more versatile on what it lets you get up to. Lori unrecommended due to bugs? Plus fixed the main issues with her (not being able to use copters, colours not changing properly). Wallkick is a glitch (and hard to fix) but it usually helps more than it hinders, but hard to perform most of the time.

I used Lori a lot, and it usually depends on the level you're playing. Some popular levels don't work so well as her, for example battle1, facing worlds, gauntlet(urgh this level), semiconductor (I know about the wallkick tricks, but the lack of a quick high jump is hindering) and jungles edge. Admittedly, I generally find Spaz better in multiplayer (except in ground force, where copter ears are a godsend, though actually I find Jazz the best in ground force where allowed) but I just find it more satisfying not to win with him. I agree with what some of the people said in this thread, it can help with taking PU's really fast. Her kick is also overpowered in streetfight, but I consider it a novelty gamemode. Learn to time high jumps with momentum, because you're going to need it. Also, all characters run the same speed. It's funny because I hear some people say Lori's the fastest, then some who say she's the slowest. It's an illusion. With the fast pacedness of online play, Jazzes uppercut in online play unfortunately isn't very useful, though there are some occasional situations and parts in some levels that uppercut reach only/faster, that Lori can't. Infact some specially placed powerups in a few levels are made to make uppercut work best on them.

TL;DR. She's good in some levels but be prepared for non friendly ones every now and then. JJ2+ fixed the annoying bugs out of her