My two cents worth..
They are both great EVs. You would be happy with either after making a choice. They are almost chalk and cheese though.
There is a very different design philosophy.
iMiEV is minimalist on the in your face features however deceptively competent in the 'just sort it and let the driver get on with driving' department. The leaf as a Mk 1 production EV is amazingly well integrated.
I too tested both at length and there were a number of key points that led me to iMiEV. (I testeed the first leaf to come to Perth) These are very much case dependent to the prospective user. You need to decide what suits your application. Folk's comments may form part of your check list only.
Price.... forget the advertised prices. The only one that matters is the deal you can negotiate. You can't compare using the prices mentioned here. I for one didn't pay anything like the advertised price. In the end, a leaf will cost noticeably more, but then it is more car !
Range... In my tests the leaf had that same range as the iMiEV though did better on range when just cruising. Hills and stop start clearly eat the energy with the extra weight of the leaf and perhaps less regen. This is not reflected in the range numbers for flat earth driving where the leaf had 20% better range. OK, just my observation.
Energy used... Given the above, for my driving the energy was going to be 24kWh vs 16kWh (50% more) for the bigger vehicle. Nothing new since we deal with this in the ICE world (2L 4 cyl vs 4L V6 etc). However when my aim is to generate my power from PV and WT and do 2 charges in a day, the extra energy was not to be taken lightly. Still, the leaf is a bigger vehicle.
I don't know what your hearing is like but the VFD whine in the leaf was like a transfer case in some 4WDs. Cringe ! They will need to work on that one.
Now for that extra money on the leaf, it came with a 3 year warranty (inc battery) and the iMiEV came with a 5 year (in Oz, 8 year US) warranty inc battery and a 10 year mitsubishi power train warranty. (note, the US dont't get the 10 year warranty). The leaf warranty could be extended another 2 years for $2,000 extra..... I'd get that if you were a leaf buyer.
What I am pointing out is that for me, warranty of the most important part of an EV (the battery) was parramount. But my discussions with Nissan showed a serious lack of concern for this EV reality.
How could I spend so much on a 'short' range EV with short range battery warranty. Thoughts of prius's with dead batteries and worth nothing at resale were in the back of my mind.
I only raise that as a concern as it was for me. Time will tell.
I have not heard of any serious warranty issues with either EV.
One iMiEV battery pack with a BMS fault was replaced in the US. A few leaf owners has experienced battery capacity reduction due to heat though not yet at warranty level. I doubt their range is now pleasing their owners. Range is small enought to start with. Spending $40k and then not being able to reach the shops in a few years is scary !
That research for me was nearly 2 years ago.
Would I make the same decision now ?
I have contemplated buying a leaf at $36990 drive away that I was offered, as a 'second car' and ditch the ICE that I keep as backup for the iMiEV.
But in actual transport function the leaf offers little over the iMiEV. In comfort and features maybe nice but I have become used to the new world of iMiEV size and driveability and perhaps the leaf just attempts to replace ICE with EV, not change our concept of vehicles ?
At this stage.... buy a leaf. Go with the numbers. Get the 5 year warranty up front. Don't buy a vehicle the colour of road grime
. Get a good price, well under $40k. all unless you want a great little EV with low energy consumption and incredibly driveable, go iMiEV, pick up a demo model under $20k.