Tricky, as both are lovely. If you're looking for something a bit more stripped down, I think I would be tempted towards the Rainbow - the lack of bi-swing with take some of the weight out of the back - and as Edward says, it's a little different from the usual. That said, I prefer the position of the cinch straps in terms of the overall body shape. I don't think you'd regret either, though, tbh.