E-stop systems are always a good cause for debate.
Ultimately they should stop movement likely to cause personal injury, and how that can be acheived depends on the machine.

We've got some quite expensive lorries at work with external equipment where some will kill everything including the lorry engine when an E-stop is pressed, whereas others will only kill the external equipment. There are pros and cons to both.
The key requirement is they should be fail safe, and periodically checked.

One question for everybody is, when did you last check all your limits and E-stop buttons worked?