Ren, two good points of reference are thebabywearer dot com (US based babywearing forum with excellent info - including reviews on many carriers and For Sale or Trade boards).

Another point of reference is baby-carriers-downunder dot com. It's an Aussie babywearing group that has a google discussion group. The founder and majority of members are in Brissy, they have regular meetups and have a loaners database.

Ring slings (eg: ellaroo, maya wrap, bear hug baby) are great for newborn carrying and bf-ing, and are adjustable, whereas a pouch (eg: hotslings, peanut shell) is sized to the wearer. Correct fit is important for comfort, so you cannot try on a pouch when pregnant. They are also no good if your partner wants to wear it and is of a different size to you. Some ring slings are supportive enough for extended wear (eg: heavier babies/toddlers and long carries) but many aren't, especially those with lighter fabrics; this is where two shouldered carriers are useful, particularly those with waist bands.

Ergos are one type of SSC (soft structured carrier). There are other types which use a similar waist band style (eg: Beco, Patapum), and others which use a mei tai style waist (eg: Connecta, Pikkolo), except with buckles instead of tie straps. Babyhawk, catbirdbaby and Kozy are some good examples of mei tais.

Stretch wraps (eg: hug-a-bub, moby) are great for newborn carries - they are soft, snuggly and wonderful when you have a velcro baby that never wants to be put down. They do take longer to put on, and have a higher learning curve, but the comfort factor is considered worth it. Woven wraps (eg: didymos, storchenweige, vatanai, hoppediz) are great for older babies / toddlers as they offer much more support than a stretchy wrap, but they are much more expensive.

Some BB threads which you might find useful:

here is a thread that I posted in recently which gave a comparison of stretchy wraps & ring slings.

Here and here are threads with lots of info on the benefits of Ergos.