Fuel economy - it's impossible to say the eAssist Malibu has better real-world fuel economy than the 2014 2.5L without testing both extensively back to back. The comparison you mention is using the outdated 2.4L with vs without the mild hybrid system, so obviously the difference would be more noticeable.
The EPA was about to reduce the Malibu Eco fuel economy to 25/36 before Chevy dropped the model, so it would have had identical fuel economy to the more modern 2.5L engine with start stop. Additionally, for 2014, the 2.5L has been upgraded with variable lift, which is responsible for 2 mpg highway and 1 mpg combined before taking start/stop into account.
Performance - early versions of the Malibu 2.5L had a programming issue that resulted in sub-par acceleration. A reflash fixed the issue and according to Car & Driver, the 2.5L Malibu is quite a bit faster from 0-60 (7.7 sec vs 8.1 sec) and also a bit faster in the 1/4 mile (16.1 sec vs 16.3 sec).
If you like your car, that's nothing to argue about. I love mine, and it's clearly outdated. Nothing can take away my pride of the only Chevy Malibu with a high-revving DOHC V6 designed for Cadillac performance.
I just love it how you guys continue to quote EPA numbers. They are numbers base on a standard drive cycle. The EPA numbers are not real and are a reference. Real MPG is going to be effected by driving style and # of passengers and amount of luggage. The Variable lift for the 2.5 started for the 2013 model.
As for performance and acceleration, it takes ~ 4000 to 5000 miles before these new Ecotec motors to achieve their maximum power(brake-in period).
I noticed a boost in power from when my car was new vs 1000, 3000 and finally 6000 miles. I also notice that the e-Assist system obtained more smoother operation as the mileage increased.
As for efficiency and economy, the 2.4 with e-Assist will beat the 2.5. And here how. Every time the car is slowed downed or stopped, the eAssist goes into Re-gen mode, store forward momentum by charging the battery. When accelerating the e-Assist system will add additional power to the engine in other words returning the power stored in the battery to assist in the forward motion of the car.
When cruising down the road, and you descend a hill, the e-Assist will turn off the gas to the engine and go into re gen. The e-Assist will modulate the re gen to maintain the current speed of the car as it descends a hill.
When ascending a hill the e-Assist will use the energy stored in the battery to provide the additional power required.
The 2.5 with stop/start does not use re-gen. All power that is used during stop/start operation for the 2.5 is generated by the cars alternator.