Brother, before buying the 1000 CC Suzuki Wagon R, I owned a 660 CC JDM version of Suzuki Kei 2007 model (Automatic transmission) with 57,000+ KMs on ODO (definitely tempered ).
Comparison:
Comfort level:
Wagon R feels more comfortable than Kei. I feel less jerks on bumpy roads while driving Wagon R than driving Kei. I have driven Wagon R at almost 130 KM/hr without feeling any jerks.
AC:
Wagon R, being 1000 CC, has a better AC to beat the heat, as compared to 660 CC Kei.
Fuel Consumption with AC:
A common misconception, which prevails among the masses, is this false notion that fuel mileage is inversely proportional to engine size, that is, the lower the CCs, the greater will be the fuel mileage. Truly speaking, 1000 CC Wagon R is giving more fuel mileage than 660 CC Kei. To put that into figures, 1000 CC Wagon R with AC constantly gives about 13-15 KM/Liter, where as the 660 CC Kei used to give around 11-12 KM/Liter. Infact, I recon the 660 CC Kei a 'fuel guzzler' when driving with the AC ON.
Ease of driving:
Obviously, 660 CC Kei with automatic transmission is easier to drive than the 1000 CC Wagon R with manual transmission.
Interior space:
Here, Wagon R is the clear winner. There is ample space both in the front and the back side to put all the goodies you need without compromising on passenger seating capacity.
Pick and acceleration:
Pick and acceleration of Wagon R is definitely way better than that of Kei.
Ground clearance:
Wagon R with its taller height possesses more ground clearance than Kei.
Engine sound:
Wagon R has a lesser noise making engine as compared to Kei.
Road Grip:
Wagon R owing to its taller height has lesser road grip as compared to Kei.
Immobilizer:
Wagon R has one, Kei had none.
SRS air bags:
Wagon R has none, Kei had one each towards the front seats.
Seat belts for back passengers:
Wagon R has two, Kei had none for back passengers.
Conclusion: As per my experience and preferences, Wagon R is the clear winner. Other users may disagree with this comparison based on having different experiences and preferences. Cheers