Asked a friend who regularly does long hikes with his infant. Here is what he had to say…
“Osprey Poco Plus. The only difference between Poco and Poco Plus being carrying capacity. They both are heavy, the carrier weight itself weighing around 7 lbs. But they are super safe and comfortable for the baby. Comparable options include Deuter and Thule. Both have significantly less storage capacity than Poco Plus, which is a major factor if one is considering backpacking with baby.”
Hope this is helpful.