Full differences shown in the article you referenced.
Basically, if you would use simple physics, it will leave you without Force, Friction, Bounce, Terrain mechanics, as well as with more simple, not as detailed collisions and weight control over your actors. Movement most likely will be less smooth, if you have rotating actors you need to collide with - that won't happen properly, and stuff like that. And most importantly - it will be harder to implement slippery floors
