Utility
The Honda Civic and the Fit can accommodate the same number of passengers.
Dimensions
Your wallet will hurt more every time you fill up the Honda Civic than the Fit because of its larger tank.
The Honda Fit and the Honda Civic compete for the same parking spaces.
The Honda Fit's shorter wheelbase may produce a less-settled highway ride but a more maneuverable feel in daily traffic than the Honda Civic.
Convenience
The Honda Fit's fuel tank will need to be replenished more often than the unit in the Honda Civic.
Cost
The Honda Civic doesn't pale in comparison to the Honda Fit with respect to gas mileage.
There frankly isn't much of a difference in gas mileage here, but if you must know, the Civic is a tad more economical than the Fit.
The Civic is considerably costlier than the Honda Fit regarding MSRP.
Handling
With their comparable turning radii, the Honda Fit and the Honda Civic quite certainly handle almost the same into and out of tight spots.
Drivetrain
The Honda Fit's engine is significantly smaller than the Honda Civic's. Keep in mind that smaller engines can be stressed more; however, smaller engines are often cheaper to fix.
Comfort
While the front cabin in the Honda Fit offers a bit more head room than the Honda Civic, there frankly isn't much of a difference.
While the rear of the Honda Fit provides a bit more head- and leg-room than the Honda Civic, there honestly isn't much of a difference.
Warranty
The Honda Fit and the Honda Civic have the same basic warranty.