Handling!
For example, many cars come in both 4 and 6 and even 8 bangers form and in general, the smaller the engine (less weight) the better balanced is the car. On larger engines they have to put tighter suspension, bigger roll bars and beeffier rubbers to achieve good handling.
My recommendation. Buy the smaller engine with the manual tranny and beef up wheel and tires and you will retain decent acceleration, obtain better handling and save on gas big time. If enough doug, improve the suspension too.