I love my ergo!
I got the infant insert for DS2 (didn't know about the ergo with DS1 until he was beyond the stage of needing the insert). We got A LOT of use out of it. DS2 was a bit on the smaller side so we used the insert for a good 4-5 months, i would say.
I got mine second hand and only paid $5 for it! I checked craigslist but im sure you can find them on other second hand websites or stores. If you dont want to forgo the money for it, my cousin never bought one for her ergo. She just rolled up a towel and she said it worked great.
I have a lot of carriers. None of the other ones you spoke of, so im sure im bias. but honestly it has served me well. Far more than any other carrier....oh and im only 5 foot 1 and it fits great :)
I like the moby for when they are wee little (like under 12lbs), however, i find nursing much easier in the ergo and far more discrete. If i had to chose between the moby wrap and the ergo, i would go with the ergo, hands down. You get much longer support out and use out of it.
