As a 50 year fan of their music, I would suggest the three essential ones (other than The Snow Goose) are ...
Mirage
Moonmadness
Nude (closest to Snow Goose in scope)
I actually find it REALLY annoying that there are two versions because I don't particularly want to buy the same songs twice on vinyl, only to find they are virtually the same. What's the verdict from those that have heard both? Which should I get?