I have used a few (hug a bub, mei tai and ergo) and I loved my Mai tai one, called a kozy carrier. It is cotton and easy to use. It us newborn to toddler and I breastfed dd in it from around 5 months (when she was self attaching and had head support etc). I used it all summer, which was a shocker in Melbourne that year (think black Saturday bushfires with days of 43 degrees).

I am getting a new ergo for this bub (I borrowed the other one) because it is more comfy for back carry.

Hth