I personally think a more accurate list would be like this:
ROBLOX
Interesting, freeform building design
Steep learning curve (Almost a brick wall)
Physics, hinges, and doodads
30% free
Also has an extremely immature (relative to other forums) forum, the other 70% is quite obviously not free, subscription-based, and the entire game has lag up the arse. Labeled as a kid's game.
Blockland (:D!)
Less interesting, fast and solid building system
Moderately steep learning curve
Vehicular physics
The ability to create games (Minigames) of entirely different genres and capability built in (Game 2.0?)
Also has a fairly aggressive forum, is completely retail, and has quite alot of 5-12 year olds plaguing the forum. Apparently labeled as a kid's game.
