Hi,
Because one is personal and the other is business, also you pay more for business plan.
You can have up to 25TB per user.
*Unlimited individual cloud storage for qualifying plans for subscriptions of five or more users, otherwise 1 TB/user. Microsoft will initially provide 1 TB/user of OneDrive for Business storage, which admins can increase to 5 TB/user. Request additional storage by contacting Microsoft support. Storage up to 25 TB/user is provisioned in OneDrive for Business. Beyond 25 TB, storage is provisioned as 25 TB SharePoint team sites to individual users.
this package also gives you Office apps and a lot more.
OneDrive community hub:
https://techcommunity.microsoft.com/t5/onedrive-for-business/ct-p/OneDriveforBusiness