For me, the i3 has the qualities Nissan could have given the LEAF but instead decided to endow it with lard-ass qualities because they were afraid 'Murcans wouldn't go for it otherwise. To wit, the i3 is smaller, and is almost 500 lbs lighter than the LEAF. That's like throwing the battery pack out of the LEAF.
In automotive design, weight reduction pays off everywhere and the weight savings are compounded throughout. Lighter weight means: brake components can be smaller and lighter for the same level of braking performance; structural and suspension pieces can be lighter because they don't have to carry or control as much weight; suspension pieces (springs, dampers, anti-roll bars) can be smaller because they have less weight (both sprung and unsprung (see "smaller brakes")) to control; motive power source can be smaller because it doesn't have to propel as much weight; ditto transmission: with less power (for the same level of performance) to transmit and less weight to propel, the gear set, drive shaft, differential, drive shafts etc. can all be smaller and lighter. Every components being smaller and lighter begets a weight saving which can in turn permit another round of downsizing of every component.
Conversely, adding weight penalizes everywhere and the penalty is compounded just as benefits are compounded for weight savings.
Range? I remember Nissan's claim of 80-100 miles per charge. I NEVER saw 80 miles. Yeah, yeah sure, those of you in the table-top desserts of AZ and South CA may have. Not me. Does BMW fudge their range numbers like Nissan? Time will tell. The availability of a range extender makes the i3 what the GM Volt could have been: simple. Besides, I fail to understand the preoccupation with making EVs behave like ICE vehicles range-wise. That's like putting a rotary dial on cellular phones because one can't get used to a virtual number pad.
Performance? 0-60 in 7+ secs is three whole seconds quicker than the LEAF, and is about what my stock 2005 MkV GTI would do.
Handling? The i3 has the same low CG and tire quality as the LEAF, but it has RWD and 50/50 weight distribution. In the twisties, I fully expect the i3 to hand the LEAF its head.
Looks? I bought the LEAF, didn't I? 'Nuf said.
Size? I am the sole occupant of the car 70% of the time. Another 29+% of the time, it's my wife and I. A tiny fraction of the time, we have luggage. An even smaller fraction of the time, I have three or four occupants in the car. Size is not an issue with me.
The biggish fly in the i3 ointment is the price. Time (and personal priorities) will tell whether the i3's price premium is justified.