They both share a lot of similar features (user ratings, tags/labels, discovering new feeds, etc.), but overall I enjoy the design/layout of rojo better. In addition to that, as far as actually discovering new things online, rojo provides a better platform for that (imo). I can see whats popular, whats popular with people in my network, etc. I've used google reader quite a bit and its really good, but I enjoy the rojo experience more.