I had the most success with the Moby wrap for the first few months. But, once our son could fully support his head and back, the babasling has been great. I just got a little tired of having to do all that wrapping with the Moby--and, as noted above, the child gets heavier and there is sag. That's not a problem, but I like how easy the Babasling is. And, now with a 20 lb+ child, it's helpful to be wearing him in the sling for just a bit more support.... (Our lift was out for three weeks, and I was so glad to have it when going up and down all those stairs!)
Unfortunately, the best advice is probably to have access to a number of different types of carrier and be able to find what's best for you. My husband was hopeless with the Moby, but did well with the Baby Bjorn. At least a lot of people put stuff up on ebay-- and you can get ahold of it there for less. Although it might be nice to have a shiny new Moby wrap-or any type of carrier- that thing is going to go in the wash so often, so quickly, it'll be less colorful pretty darn quick!