Services like Buffer or Hootsuite were made for marketers and not photographers. That is the main difference.
Here are some of the tasks you can do with Pixbuf, but not with other services:
- Pixbuf supports more services than others
- sharing to photography services like 500px, Flickr, Youpic or Instagram
- focus on the quality of your photo - we do our best to upload as much good photo as we can with the limitations by the services
- you can see photography analytics about your photos - which of you photos are popular, why and on which social networks or photography services
So, if you are a marketer and your main focus is to publish text-content with images, use Buffer of Hootsuite. If you are a photographer, use Pixbuf. Pixbuf is Buffer for photographers.