Why enable/disable collision when you can just ~

Why enable/disable collision when you can just enable/disable the physics behavior for that object ?

They seems to be doing the same thing.

One option requires you to use a slower version of physics instead of Box2D asm.js so why not just disable the behavior ?

What conditions require anyone to Disable the collision instead of just disabling the physics for that object altogether ?

Because if you have say Object A that needs to collide with Object B, but not Object C. You would disable collisions between A and C, allowing A to collide with B.

If you just disabled the physics behavior of A, then A wouldn't collide with B.

Edit.. also, perhaps C should collide with B as well.. You wouldn't be able to just disable Object C.

Thank you