I won't say which is the best because I obviously can't try all the carriers but ErgoBaby360 works for me.
I have very bad lower backache that spreads to my hips and knees whenever I carry my baby without a carrier. It's an old problem plus I have a bad posture. Ergo corrects my posture and distributes baby's weight evenly for me. Every time when I have pains, carrying baby in the ergo makes me very relaxed and happy.