Ergo vs Beco Butterfly 2?

[Sew_Sweet]

For those who may know - what is the difference? Which do you prefer and why? I want something that can grow with my baby. he is only 3.5 weeks now and we are using a sling but I also wanted a carrier like this. Someone I know is selling a Beco but I am unfamiliar with the brand and have never tried an Ergo either but I know they at least look similar and are at a similar price point.

Also how much would you expect to pay for a used Beco Butterfly 2 that has "only been used a couple of times"? Are there fakes? How can you tell? Thanks.