Hi B.,
I can only tell you that the Ergo carrier is the BEST! I have a very large boy, 35lbs and 1 yr (he's been 33 lbs for about 5 months too). The ergo is a backpack and front carrier. It is very good for the child's spine, and hips.
There is a mommy who does our stroller circuit training workouts with her 2yr old in it!
It is super comfortable and very sturdy. I plan on using this one with all my children (2 more planned). There are numerous ways to wear it (just watch the DVD).
And the kids don't mind facing mom, that's where they want to be anyway!
I cannot tell you enough how much I love that thing. I swear I don't own stock in the company, but I would if I could!
PS: we tried them all: bjorn, moby wrap, side sling, traditional sling - he out grew them all. We even have a backpacking one...but the ergo wins everytime.
Good luck. It's worth every penny.