What's the difference between a Virgin MiFi and a Sprint MiFi?

Same device.  Same network.  Same company too.  The difference: one of them comes with Sprint's pricing: $60/month for mobile broadband and a 5GB limit.  The other comes with Virgin's much more generous prepaid plan of $40 per month and no cap at all.

The market says: The Virgin branded one is worth $150 on eBay and the Sprint one is worth about $50.  The Sprint one does allow some roaming on Verizon where Sprint lacks coverage, but the market clearly thinks that's not worth much at all.