RE: Sling or Carrier?
Some of it depends on how much carrying you're thinking about doing. A frequent complaint with the Bjorn is that when baby gets above a certain weight it is just too hard on the shoulders. Also it is not cheap!
I started with a New Native pouch, but when my baby got above about six pounds it was just too much weight for my neck and one shoulder, which is another consideration. I have been much happier with my Moby Wrap and Ergo since they use both shoulders and your waist for support. I agree with the PP that it can be hard to know until your baby is here. So you might want to start with a fairly inexpensive sling or pouch (I know the New Native is only about $40 or you can get them used for less, and there are lots of others similar or cheaper) and the Moby wrap is only about $30. See what you like and go from there.
Two sites with some good info and comparisons are TheBabyWearer.com and Peppermint.com.
HTH!
Nancy, mom to
DD1 5/04 and DD2 3/07