We have an Ergo, which I love and is very easy to use. My son is 11 months old and about 21 lbs, and it's great. I'm still trying to get the hang of getting him on my back in it...I always sit on the edge of the bed or couch when I do so if he falls back, he won't get hurt. We also have a Beco Butterfly 2 which is good too. It's a little trickier to getting all the straps adjusted, but it's also very comfortable and a little easier to get him on my back. Hope that helps :)

I Love my Boba!!! I also have a Beco and it's great too. If your son fights back carries the Beco would be the way to go since you can safely secure him in the carrier BEFORE lifting him to you back. I bought this when I had my second so I could do back carries early on (around 3 months vs 8 months), but My 2 1/2 yr old 30 pounder can happily ride in it just as well! I have to say the Boba has a larger seat and overall is made more for a toddler. I have the Boba 2g. I've tried the 3g and of course newer is always better, but if you can save enough money the 2g is just as great. The ergo in my opinion just wasn't comfortable- for me or my husband. It has a lower back and felt like my lo was falling back. Hope this helps!