I've got an Ergo, Toddler Patapum, (SCC's) Maya wrap, (Ring sling) Hopp (Woven wrap), Hotsling, (pouch) Kozy (mei tai) - there've been several others in and out of our house, I'm taking uhmmm maybe them all
High and tight is really important to babywearing, they are closer to your center of gravity, less pulling on your shoulders and back.
The main problem I see with some carriers is that baby is hanging as apposed to sitting in the carrier. Where the carrier puts babies weight is important too, you want all that weight spread out evenly and mostly on your hips.
9 months is a great time to move to your back, bigger babies are going to be a strain after awhile on your front anyway, no one carries a heavy backpack on their front!
There have been good carriers recommended - you would probably like a soft structured carrier, since the bjorn is what your used to. There are only about 3 carries to do with these (front, hip and back) but they are simple on and off, dad likes them, grandma can figure them out.
Most people who try on an Ergo, Beco, Patapum, or other SCC are shocked, the baby almost feels weightless!! I've had people run me down asking about my carriers lol