E8372 needs to plug into USB port and not every devices have them. And even if you use a laptop with USB port. It limits where you can use your device as with Digi 4G, you want to be as close to the window as possible to get the best experience 

a MiFi with own battery like the one Digi provides can be placed at the spot where reception is the best and you can use you laptop tablet from anywhere you are comfortable with in the house.

USB modem need pc/ router to work. mifi not.