the contract is only 12 months and well worth it as the same model fetches way more on the market

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.

rule out wall adapters and car charges as those restricts the location where you can place the MiFi.

Which left power bank, which is a very reasonable choice except that I don't already have one. Never feel the need to get one as I never have problem with my phone battery being not enough and most of them are too bulky to be conveniently portable.

Just accept that all the different different devices out there exists because people have different needs. I merely comment that by accepting a 12 month contract you get a device that goes for over RM300 in the market for RM9 per month. Which is worth it if it fits ones needs.