From my own experiences and what I’ve researched there isn’t enough evidence that exists from either that dictates there there are these separate “planes” of existence.
From my own experiences, I’ve experienced realities that looked very similar to this physical reality, including areas which I mostly recognize… and I’ve had experiences in realities which are nothing like this physical reality nor are anywhere I recognize.
I surmise from this that what people label as an “etheric” projection is a projection where they are in a non-physical environment that they recognize to be this physical reality… when it’s very strongly possible that all they’re experiencing is a non-physical environment heavily modified by their own consciousness.
See, I believe that people are interpreting their experiences too literal. Robert Monroe did this at first and while it “seemed” like it was correct at the time, he later figured out by his third book that what he was experiencing could not be taking literal. Just like you can’t take a dream and interpret it based upon the literal translation of what you’ve seen/experienced.
So, back to the “etheric” projection… I think it’s strongly supported by the many reports that I’ve read and what I’ve directly experienced myself that reality works much in the same way it does while physically awake/aware. We each experience a non-physical reality (consensus probably) and we each interact with that reality on an interpretational level, meaning that what we experience we must interpret first in order to experience it. While we’re doing this through our projection, we’re not only interpreting our own experience, but other consciousnesses in the “area” (quoted because it’s loosely meant) are also creating and pushing their creations upon others as well… this is why I believe we get reality fluctuations. The further away from the more familiar places we get (ie: our bedroom, house or street) then the more reality fluctuations kick in. Simply put, the source of them is from other consciousnesses working against your own creations.
Going back to the original question… is there a difference between etheric and astral projections, I say only if you believe there is. I don’t think there is any objective evidence out there that supports the existence of different planes. I believe it all comes down to personal interpretation of the experience and what that particular person has experienced or read about previously.