I've only used a Maya Wrap ring sling with new babies, because I didn't know about other carriers until my second child was a bit larger (maybe three or four months). I don't have a bad back, and I was not carrying her all day long (at home she would be in my lap instead) so it was tolerable having the weight only on one shoulder; if you have a bad back to start with, I would stick to something that uses both shoulders like a wrap. I found a ring sling was good to breastfeed in public in, once I knew how to do it, but it took a little practice. The tail is handy for covering up so you can nurse in church or a hardware store or whatever without people knowing. Also, my husband was able to wear the same ring sling whereas we would have been different pouch sizes... not that he did it very often ;) but I could duck out of the sling and put it on him with the baby still inside and then adjust it to fit ok on him.
You can have your cake and eat it too, though - buy a nice ring sling, and make a stretchy wrap yourself with these instructions (no sewing required) : http://mamatoto.org/Default.aspx?tabid=121 If I could go back in time, I think I would do that. :) I haven't ever found an inexpensive fabric in a store that would be comparable in comfort to a woven wrap like a Didymos or even an Ellaroo (and by the time you're paying for a long piece of more expensive fabric, y'see, you might as well be buying a secondhand Ellaroo) but the smaller and lighter the baby, the less of an issue this is, I think. Then if I liked the wrap better, I could buy one later without it being a leap in the dark (that is what I did when I found out about other carriers.. made one myself first to see if I would like it, then bought a prettier one than I could make ;) )