After a long stretch of borrowing a freestanding Hubba from a less active friend, I’m getting ready to pick up a shelter of my own and I’m thinking about a Tarptent Rainbow or Moment, the likes of which I’ve never used before. I don't know much about them beyond the info on the official site and the glittering reviews on forums like this one, so explain it to me like the single-wall newb I am: what differences will I see? What am I giving up and what do I gain along with the weight savings? And what's the functional difference between the Rainbow and Moment?