To me, it depends so much on the age of the babe. For a newborn, I think the easiest/most comfortable is a stretchy wrap like a Moby, Hug-a-Bub or Cuddly Wrap. You can leave the wrap on and pop the baby in and out throughout the day, you can BF discreetly in there, and I loved the comfort of a two-shoulder carry (pouches were great, but not as comfy for me).
And then after 6 months, back carries became so essential to me--I found a buckle carrier easiest (like a Beco, Ergo, etc.), but a Mei Tai is a great option too. And many people find woven wraps (like a Didymos) the most comfortable of all--it just takes some practice to get the hang of it.