Leaf and Niro are almost identical in height and width. Leaf technically has a better CoD. Both use 17 inch rims. Weight is pretty similar.
Many tests seem to show the EPA difference (215/226 to 239 ..though most tests use the SL, so 215) to understate the range difference between the cars.
The batter is bigger, by about 3.5 kWh from what I can tell from the UDDS tests. That would explain about 12-14 of the 25 miles epa difference.
Either the power mapping help improve efficiency, or the power train just more efficient.
Interestingly enough, Niro (on the car wow test) on a published range vs. actual did much better than the M3 LR. On a proportionate basis, even the Leaf would have out run the M3 SR+, and the Niro got close to the M3 LR.
I know we are off topic. Apologies.
2019 SV Plus Silver 6/19 purchase 7,000 Miles
2013 Leaf SV
100 Mile Club Member (Number 87)
Max distance on 13 Leaf: 120 miles
Max distance on 19 Leaf: 242 Highway 4.5 miles/kWh