Both vehicles are 6-speed manuals. Interestingly, the F30 is heavier with its 3412 pound curb weight than the E90 although just slightly by 26 pounds. The N20 four cylinder also affords the F30 with a little bit less weight on the nose as it's 49/51 front to rear weight distribution compared to the 50/50 for the E90 shows. The length of the N52 inline-6 in the E90 328i playing a factor.
Performance wise the new 328i is simply faster. 0-60 in 5.6 seconds for the new car versus 6.0 for the E90 and the 1/4 mile coming in 14.3@100 for the F30 versus 14.7@96 for the E90. Definitely significant and the 0-100 number really tells the story as the N20 gets to 100 miles per hour a whole two seconds faster than the N52. Despite being rated only 10 horsepower higher at 240 the real world power difference is much larger than indicated by BMW.
Additionally, the fuel economy figures show why BMW made the change. The N20 has more power and torque yet gets better mileage. 27 mpg in Road and Tracks testing versus 25 mpg for the N52 based E90. 2 miles per gallon plus better performance, difficult to argue with.
Road and Track however does argue the E90 is the better car. Why? The steering feel is slightly more communicative. Also, the N52 is the better sounding motor in their opinion. Picking the E90 over the F30 based on the engine sound and steering feel? The steering feel point has merit but the performance gap simply is too large to ignore. Hard to agree with this decision and this statement:
"In terms of real-world speed, the two cars are evenly matched, posting identical results on the 5-to-60-mph rolling-start test, where the naturally aspirated six's instant response beats the four's turbo lag. On the conventional 0–60 run, the more powerful four-banger is 0.4 second quicker—and as speeds increase, the new car pulls ever farther ahead."
A two second difference in 0-100 times means in real world comparisons on the highway it really is no contest. From a stop, it's no contest as well. The only time the cars appear evenly matched is when the N20's turbo lag is used against it. This is a valid point but it is only a single situation that evens the cars as in all others the N20 offers superior performance and efficiency.
A naturally aspirated BMW inline-6 will pretty much always sound better and be smoother than their turbo four-cylinders. But the E90 is not the better car and the N52 is not the better motor. The N52 is probably one of the weakest examples of a BMW naturally aspirated inline-6 that can be chosen. When one experiences the magic of an S54 high revving BMW inline-6 in an E46 M3 that is a whole different ballgame. In an example using base 3-Series cars where power, torque, and acceleration are all improved along with efficiency BMW's turbo decision makes complete sense. Road and Track's decision would make more sense if they were comparing a naturally aspirated previous generation M car to a new turbo M car. Efficiency is not at a premium in a performance model which should be a razor sharp responsive Ultimate Driving Machine.