I have the hip hammock. I never tried the other. I found the hip hammock easy to use and comfortable. The thing about this is that you really do have to keep your child on your hip (like you would if you were carrying him/her), as opposed to slightly in front or back. It may seem obvious to some, but for me, in reality, it was a little difficult to make sure DS stayed perfectly on my hip. My arm got in the way. When he was on my hip, it was very comfortable. If you push him to the front, even a little, it throws off your center of gravity and takes a toll on your back.
For the few times that I've used it, it was very convenient, especially to WDW. However, the material makes it very hot for the child. Keep that in mind. For the price and convenience, I'd buy it again. I'd just take extra care to wear it properly so that your back doesn't get strained.