What are differences (if any) from an erad mid drive kit and a Bafang kit?
An e-rad kit is a rebranded Bafang kit. According to lectric cycles, they had Bafang add a port to plug in the optional gear change sensor which lectric cycles currently have a monopoly supply. Bafang also modified the firmware to support the gear change sensor - with other gear change solutions out there, like a "clutch" button on the handle bars, there is a relatively long delay after cutting the power to change gear before power is restored - it's annoying. Those other solutions all take up a brake sensor port too.
The newer e-rad kits will have new mosfets in the controller too but according to em3ev, these are now going to be standard in all new Bafang kits - it will take some time for these to work through the supply chain though.
E-rad has some other custom firmware tweaks too.
In my opinion, the only meaningful difference, is the gear sensor which no one else comes close to providing in these mid-drive kits. For you that may not be a big enough deal to accept the extra cost - for me, that's lived with a BBS02 without it and mangled a chain as a result, if I buy a BBS02 again, it will be with a gear sensor.