I had 2 different types when I had Indie - a Tomy Freestyle Carrier and a Hotsling.
Tomy freestyle carrier was great and comfortable to wear. Indie looked very comfortable in it and I used it until she was about 6 months old (she was little for ages). To start with she faced me and then when she was bigger she sat facing out so she could see what was going on. The only downside to having one with a summer baby is that they may get quite hot in it. Indie was born at end of October so it didn't matter.
I think Indie preferred because she could lay down and it was handy for breastfeeding. I found the sling much easier to put on than the Tomy, and much easier to get the baby into a sling than a carrier but not so comfortable to wear if you are going to out for hours.
Hope this helps x