but are any of my initial impressions correct?
getting both isn't out of the question but it also seems pretty redundant.
Star Citizen will, probably, have a more 'grand scheme' feel than ED, but overall they will be very similar. ED will also have landing walking around on stations/ships/planets, but those features will come in an expansion. It's worth noting that it's not unlikely that that expansion will come out before SC is released.
I have reservations about Star Citizen, because their development process has apparently been incredibly slow, and when they finally did release something, it was just a very simplistic space combat arena.
Over all, I much prefer the massive scale of ED, simulating the entire universe. If I were in your shoes, I'd go for ED, simply because I can play the game now. Then I'd buy SC when it eventually came out, probably in a year or two.