Then differences can occasionally be difficult to spot.
Mainly for those with more psychic ability.
Strange to say, but yes, it does get more difficult to tell the difference if one has more psychic ability.

It's rather easy to imagine.

For one, think about what they are.
Astral Projection is the temporary release of the soul, of which is attached to the physical body.
Etheric Projection is the release of the soul, of which is not still attached and takes over the vital signs of the physical body leaving the physical body clinically dead.
EP is often confused with the Near Death Experience (NDE).

Psychics and regular people alike may see either, and either can not be differentiated except the capacity the subtle body has to effect the physical plane.

Meaning, the subtle bodies of astral projection and etheric projection are exactly the same except one (etheric body) is much more dense therefore more so capable of effecting the physical plane of existence.

Therefore, say in the case of a medium, they will be able to see and sense the astral body nearly as well as the etheric when a regular person with no such experience will most likely only be able to see or sense the etheric body.

* For those with more experience in the paranormal field:
~The etheric body can be compared more to the density and capacity of a poltergeist

While as...

~The astral body can be compared more to the density and capacity of a specter