Rubber mulches can smell, like rubber, which many people find objectionable. Since I tend to not walk on mulches I would not know whether rubber is easy to walk on.
There is some research that indicates rubber mulches are hazardous to you and your soil, but the most important thing is rubber mulches do not contribute any thing worthwhile to soil.

At the risk of being rude.
Why would anyone use rubber mulch in the garden or compost!
To answer your question.
Fort Jackson in S.C. has rubber mulch on the jungle jim training area, inside the 1/4 mile track. It is easier then walking on gravel, for a small fall it is better. But if you are running & fall, the rubber can cause burns.
They use it because it will not rot in our life time.
It is bad in my way of see the garden, no I am not an activist.
I just think rubber should not be chopped up & put near growing plants, Plastic mulch is bad enough.

It smells to high heaven. Because of the high levels of zinc and other chemicals, it should not be used around plants. It does not last forever, as is claimed, by the way.

Here is a link that might be useful: more information