I worse DS because it made life a million times easier (and he loved it). I used a ring sling or a moby for just whatever around the house. When it came to outside events (once he could hold his head up) I used an Ergo. He still loves to be in it; but is too heavy for me so H will carry him on his back.
I use a Moby for DS (2 months) and love it. When DH and I are out together, he also baby wears our DD (15 months) in an Ergo. We used both with DD from 2-7 months old, and then switched fully to the Ergo. We'll probably get a second Ergo in the spring so that we can keep wearing both babies when we are out together.
Mommy to N (3), J (2), and C (10 months). LO4 is due in mid-September.
We tried the Moby with DD#1 - didn't like it since it took so long to put on, and I couldn't get it tight enough. She was born in May, and we found the Ergo with infant insert to be too hot for the summer...so she lived in the baby bjorn (we had one, and after the 2 others failed, that was what we went with - I know it is not a popular one!).
With DD#2, I used the Maya Wrap ring sling a bunch, especially to nurse her while on the go. LOVED it. Also used the Ergo since she was a winter baby and wasn't going to overheat in the infant insert. Still use it for times when I need my hands free (we went to a fall fair today, and DS and DD#1 were all over the place - DD#2 hung out in the Ergo so I could keep up with the other 2!) We kept the Bjorn in the car for trips to the grocery store, etc...it is definitely not as comfortable for me as the Ergo, but she loves to face out!
Check and see if you have a BWI group near you. They have lending libraries that will allow you to try out a whole bunch of different carriers. I have way too many personally but if I had to choose I'd keep my Lillebaby and a ring sling.
Re: Baby carriers