I think trying to find something that's all things to all wearers is kind of an exercise in futility.
The Ergo will work better for the dad in your scenario - I'm about 5'8" myself and it was my go-to carrier after my DD outgrew being comfortably wrapped. I also have a toddler sized KinderPack, which I love.
For a petite mama, I have to 2nd the Pikkolo (with support belt!) but really love a wrap best for the newborn stage.
Also, is there a babywearing group near you? If you're not sure, thebabywearer.org has resources - it's free to join, but I think you need to be approved?
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Liz
DD (3/2010)
"Make mistakes! Get messy!" - Miss Frizzle