Since good fuel economy is a key consideration for you, a diesel will fit your needs better.
Among your options, the Mahindra XUV700 diesel is the most well-rounded choice. Its diesel engine is smooth and powerful. The XUV700 mileage is 17kpl for the manual diesel engine, which is fair for an SUV of this size.
The Hyundai Creta is smaller, and its diesel engine is less powerful. Creta mileage is 21.8kpl for the manual diesel; therefore, fuel economy will be significantly better than the XUV700's in case your decision entirely hinges on fuel economy.

