Well, that depends on the driver. In general, a ported design will go lower than a sealed design with the same driver.
However, some drivers will do very very well in a sealed design and with a lot of linear excursion can handle some very agressive eq to boost the low end.
It also depends what you believe about the audibility of distortion at low frequencies. Sealed subs tend to show more distortion the lower they go. EQing would further push up distortion.
Here is the same driver with two sealed models added. The one with the highest roll off is sealed with no boost. The blue line is with 6db of boost added at 25Hz. You can see that the ported designs outperfom sealed all around. This driver does best in a ported alignment though.
