I'm an Ergo person for about 5 months old and up, but don't love the shorter body & fairly bulky straps of the Ergo when compared with the Boba 3G.
The Boba straps lay a bit flatter ... and, as a bonus, the belt (which should really sit on the hips in a back carry) adjusts to accommodate a lot more waist/hip sizes than the Ergo does.
If your baby is tall in the torso, go with a longer-bodied carrier - Boba, KinderPack, Olives & Applesauce, Tula - over the Ergo.
I tried the Gemini once and do love it quite a bit, but it wouldn't be my first choice for a 22-lb older babe.
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Liz
DD (3/2010)
"Make mistakes! Get messy!" - Miss Frizzle