Precautions: Moby Wrap

Hotslings Stretch Sling or Moby Wrap Carrier

Hi Moms- I'm looking for some input on slings. I didn't have one with my first child, just a Bonjourn. I'm looking for something I can use from birth that will allow me the use of my hands for my 2 year old. I found that the Hotslings and Moby both have great reviews. My concern with the Hotslings is what size to order. Many reviews say the sizing didn't work for them. My concern with the Moby is that in the instructional videos it looks a bit time consuming to put on since it is not preassembled. Has anyone used either of these...