We offer two electric folding bikes, which are the Tern Vektron and the Brompton Electric. Both these bikes are suitable for different people, so here's a brief comparison.
If you're looking for a full power folding electric bike, then you should consider the Tern Vectron over the Brompton. This is because if you're going to be carrying a lot of stuff and you're going to be touring, then it's the better bike because is has a full fleshed Bosch Electric motor system. This means the Vektron is better for longer distance riding as well, and going to be more capable at carrying loads up hill as well. It really is the bike for people who want a fully fledged ebike but cannot afford the storage space that it would usually afford.
In true Brompton fashion, they had to do things a little differently. Their new ebike focuses on being a lightweight and portable bike rather than being full power, so that it matches the rest of their design philosophy. It has a battery pack that comes in a small bag, which you disconnect from the bike and carry by hand when it's folded. It uses a high quality front hub drive motor, to keep the to keep the weight down, not just for when it's being ridden, but also for when it needs to be carried. This also keeps the bike thin, which is necessary as it's bike that needs to be folded across the drivetrain. The Brompton also uses very small 16 inch wheels, which gives you an advantage due to the hub not slowing down too much, meaning that it should still give you full power at lower speeds. It's really the ideal ebike to hop on and off the train or to throw it in the back of the car.