Apart from having more storage capacity, why not just get a complete portable one that uses 5V and doesn’t requires you to power it with a plug? What advances does a big 12V external hard drive have against a smaller fully portable 5V HDD?

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I have a Seagate One Touch 5TB and it’s great but I want another one probably with more storage but from what I’ve seen only Seagate’s Expansion Desktop drives offer more storage than 5TB.