Hi, funny you ask that as i had the same thought a month ago. I actually reached out to both of them to clarify the defining difference. Populous never responded and at least HIVE had the decency to respond (although in pretty bad english). Based on that HIVE would win from my perspective. See below their answer:

"thank you for reaching out with a question.
If I understan correctly, Populus´s aim is to become invoice exchange platform, where you van buy & sell invoices. However, Hive is aiming at sth different:
Hive uses invoice factoring to get the invoice entry into the system. System will than have a fund running and will be opened to peer to peer financning like an exchange, however end goal for us is - credit scoring of the companies and 3rd party auditing.
Hive will be an ecosystem of invoices that will be used for credit scoring and 3rd party auditing. Populus aims to be invoice exchange.
To kick start we will have the fund buying invoices in crypto, however latter on it will be an eco-system with data offered to the market.
If you need anything else pls don´t hesitate and let me know!"