Originally posted by Onjin
Yeah, I tried Knex out about 6 years ago. Shitty. Never tried CD, looks too fast from videos.
You can make a pretty decent screamin' squirrel with K'nex, but you have to be fairly creative (and well-practiced with the kits). It's definitely not good for any rides of larger scale. I built entire amusement parks out of K'nex in my youth, but they didn't have any large coasters due to friction issues.
Coaster Dynamix does, in fact, look too fast to be "realistic." This is because gravity is constant and cannot be scaled to fit the model. However, I think it is best to have realistic friction coefficients and deal with the overly powerful gravity, because the alternative is to not be capable of making the correct layouts at all.
To summarize: K'nex has high friction and loads of physical constraints (only some of which can be overcome by clever re-engineering), but it looks roughly right to the eye when run. CD allows you to create a realistic layout with its superior physical properties, but it doesn't look as "right" because gravity's a bitch.