The response exhibits a shallow rolloff (3-6 db/octave) from a certain point, in this case 40 hz, down to the tuning frequency. The F3 is a little higher and actual frequency response isn't as flat, but if you combine this with room gain, an EBS will go usually go lower and flatter.

the 4.78 cuft box will be completely flat to 37 Hz, but will rolloff quickly below that frequency. Not nearly as good for subwoofer duty.

Neither box design is superior IMO, just good for different applications. If you choose the right woofer, you can get flat response to 20 Hz without even doing an EBS alignment.

Adam