Better looking stitches- Being a machine dedicated to only embroidery means the quality of the embroidery will be better.
Less threading and rethreading- The time it takes to complete projects with different colors will be shorter by not having to rethread after every color change.
Easier/Larger hooping- Able to attach bigger hoop sizes and because of how the hoop attaches to the machine, it makes it much easier to put on.
Speed- Faster stitch time for multi-needle even when both machine are set at the same rate.
More options for embroidery- You have more options for what type of medium you wish to embroider on.