I just checked my email and have an update that mama bargains has Beco's for 50% off.
They'll go quick, if you want one act fast!
I have both (I have a slight baby wearing addiction) and I actually find the Ergo more comfortable and easier to use. Your best bet is to go to a store that specializes in baby wearing and try several carriers out, pick the one that feels best to you. They all sort of have advantages and disadvantages, and are good for different reasons. A woven wrap is great for versatility of use, a sling is great for quick in and outs, and the soft carriers like the Ergo/Beco are great for longer wearing, hikes, and ease of use.
ETA: An Ergo will get you from newborn to toddler wearing. Not sure about Beco.
I have a Beco Butterfly 2. One thing I can see being an advantage to the Beco (butterfly 2 anyway) is that you don't need to buy a seperate insert to use for the NB stage. Maybe I will like it will a smaller babe, DS was about 1 by the time I got the Beco and I found I had a hard time wearing him as comfortably as I could in the Ergo. The Ergo fit me better and put more weight on my hips rather than my shoulders/back.
I have an "original" ergo. They do have a few different styles now, they didn't when I bought mine. The varoius styles are here: http://store.ergobaby.com/Baby_Carriers
I bought my SIL the Sport. She likes it as well. She had a baby bjorn with her first and didn't like it. I bought her the Ergo and she used it a ton for her second.
If you get an Ergo, you will need to buy the "heart to heart" infant insert for the NB to 4 or 5 months stage when baby can "frog" it's legs more comfortably (when the hips can handle this). I actually loved the insert as it held DS really snuggly and gave good support for his head/neck.
Just be sure if you get a carrier it is one that supports baby properly. A lot of carriers out there (including the baby bjorn) are bad for baby's spine and hips. This isn't a scholarly article, but they are easy to find and a few are referenced at the bottom of this blog post
I have heard from others that the Beco may be better if you are petite. I am tall and slim but have broad shoulders and am not "skinny". DH can also wear the Ergo really comfortably and likes that it isn't "girly" like my woven wrap or sling.