When I was shopping for a used EV, the FFE was a contender for me - mostly because nearly new, fully-loaded ones were going for ~$13,000. If Ford had done a better job packaging the battery, we may have bought it. We drive around with our dog in her crate, and being able to put the kennel in back behind the rear seats (without folding them down) is important to us. The FFE is a good car but felt cheap when compared to the B250e.
The FFE doesn't really have a cargo area. What it is would be better described as the battery compartment. When the FFE was making it's rounds on the car show circuit, the trunks were locked and the cargo covers were pulled for a reason. I think Ford may have sold a LOT more FFE's if they engineered the battery into the floor (if that was possible) but their goal was never to sell very many of them. The same could be said for the Mercedes EV as both the FFE and B250e are textbook compliance cars, but the Mercedes is at least a more practical overall package.
I think there's a lot of guys that make a lot of sacrifices to save a buck but (at least for us), spending that extra $10K for the Mercedes was a no-brainer. A year later, used 2014 B250e's are still going for about what I paid for mine. Can't say the same for the Ford.