Check out this amazing chart on The Portable Baby. She is down on the Bjorn for health reasons for the baby and wearer, and down on all single side carriers for health for the wearer (like pouches or the Scotababy).
Of the Soft Structured Carriers, she doesn't like Ergo (which I love), but says it is because of the company. Her reasons sound solid. She makes an argument to try the Beco carriers, or the Boba 3G (I had tried the 2G before and didn't like it, but it seems they have solved these issues). The Beco Butterfly 2 seems nice, with the holder for baby inside the carrier. The Beco Gemini also seems nice, but for smaller babies or outward facing up to 20 pounds.