I drove and research both, and the i3 is just a brand, I don't feel it is a value, no even BMW feels that way when they depreciate the car 46% in 3y, 36% in 4. Interior finish of the i3 is too basic and simple, almost prototypish. Externally I can live with these doors, the paint colors and choice of black on the top I just don't like, but the worst are the wheels that use some ridiculous bike size tires with no spare of course and a repair kit instead. I could bear that if the tire size was standard, but it is not, and if you have a flat there is good chance that you will have to be towed to a BMW dealer to replace at BMW cost your tires, all assuming they have stock.
The driving of the two cars felt great, nice acceleration and I didn't feel the i3 much faster, only more noticeable the deceleration. The top Leaf has similar equipment than the i3, in fact I noted the i3 didn't have steering wheel heater. Also the i3 technology package allows to monitor and control your car with only iPhone. The Leaf carwings does have apps available from iPhone, Android, and even Windows Phone. Because I am an engineer, I even contacted BMW factory in Germany to see if they would facilitate an API (software tools) to develop in other phones, but they are hermetic, so this won't change much or open to other useful apps any time soon.
Externally looking from the side, I like the i3, but from the front, and back specially looks weird, these tiny tires remember me the old cheap Citroen 2CV that existed decades back in Europe.
On top of that, Nissan has much better deals with, invoice price, rebates, 0% interest, or better lease devaluation gap that get you a car for less than half...
I am trying to get a Leaf now, perhaps in a couple years BMW comes with something more realistic. I am also watching closely the Mercedes release, but as today is vaporware to me!