I've had an i3 for almost 3yrs and test drove the Bolt recently. I think the difference in the regen is the motors. The regen in the Bolt and the i3 will bring the car to a complete stop, whereas the Tesla regen fades out at about 2-3mph. My understanding is that the Tesla has inductive motors while the i3 and Bolt have fixed magnets. The fixed magnets are operating at any speed, the inductive motors don't have any resistance at very low speed. But more important is the regen from 15mph+ and I believe the Tesla has plenty of regen at those speeds. The bottom line is efficiency. My i3 weighs a little more than half (2,600lbs) of the Tesla's 5,000lbs, but uses about 240Wh/mi, while my MS averages about 315Wh/mi in 70% / 30% around town / freeway driving. So the i3 is about 50% of the weight but uses about 77% of the energy. On a Wh / pound, the Tesla is much more efficient. And the Tesla's superior aerodynamics are not an issue when the average speed is 30mph. That said, it is a little annoying to have to always use the brake pedal on the MS and I enjoy the ability to be entirely "one pedal" in the i3!