It's worse than you think for the marines. Only if you play "Primaris" do you get all of the cool new toys. "Firstborn" Marines(the old marines that you know and love) seem to have frozen themselves in time at around the 7th edition. So they have a few flyers that were added to their list, but that is it. I have two chapters of old school marines, Crimson Fists and a homemade chapter that I am fleshing out. I for one won't be going the primaris route at all. Their models don't appeal to me, I don't like the story line of them, and I don't like what I have seen so far from them game-wise.

As far as the Banshee's I would wait until you get a codex out on the Eldar first. Primaris Marines were not the be-all end-all, and I doubt that they will continue to be as well.

I did get a chance to read the rules a few months ago, and the best way that I can describe it is "watered down." That can be a good thing in that you don't really need to remember much for the rules, but if you are looking for more detail in your game, then you may be disappointed. I would prefer to get a few games to pass final judgement, whenever that happens.