The difference is subtle, but the result is quite remarkable and obvious.
From what I can tell the common difference between the two nethods, is that astral projection is more about "visual" immersion and visualization; etheric methods are more tactile and require no visualization, because it's progression is more dependent on physical factors, than mental.
Alost everyone who has had an etheric projection (including myself) has not ever had to visualize anything - it would happen on it's own, complete with the "exit" stages, such as buzzing in the ears and the feeling of suddenly falling/rising. While astral projection has no "exist" stages, but the person merely finds themselves in another realm, that is too fantastical to be physical. Keeping in mind: astral projection deals with "non physical" realms, so that experience is far more subjective, which is why I said it is like a dream and not like being awake. When shamans/witches "travel to the Underword" they are astral projecting.
Rememer, it is common for the methods to get mixed up as well as the writers to not be aware of the dinstinction (mainly from doing one more than the other). This does not imply there is no difference, but the fact that such information is obscured.
An example of a real astral experience would be someone having an "adventure" in some unknown land, with wizards and castles and faeries. An example of a real etheric projection, would be someone floating around thier apartment complex, or just walking around their block.