ExEC
How Ex d contains ignition
Ex d, or flameproof, accepts that an explosion may happen inside the enclosure and builds a housing strong enough to contain it.
How Ex e prevents ignition
Ex e, increased safety, takes the opposite approach: it prevents sparks and excessive temperatures from arising in the first place.
Choosing the right concept
Neither is universally better. Flameproof suits motors, switching and anything that arcs; increased safety suits terminal boxes and junction enclosures.