Given the same driver sensitivity and power capability, ported subs should theoretically be twice as loud as a sealed sub thanks to the port. However, loud is not everything. We also experience bass through pressure waves, and the sealed sub does a better job of producing pressure waves.

My "T-Rex" audio track is from a 1994 Telarc Cincinatti Pops CD album entitled "The Great Fantasy Adventure Album". The album has a warning that there are infrasonic frequencies to 5 Hz on 5 tracks which include "T-Rex", "Jurassic Lunch" (another T-Rex), and the "Terminator" theme. These have proved to be excellent test tracks for evaluating a sub. My impression is that a sealed sub couples more energy to the room than a ported sub, although both types can be very impressive with these tracks.

The SQ of both ported and sealed subs can be degraded by design compromises. It's somewhat easier to design a great sealed sub, but the sealed design is no assurance of better SQ. A poor design is a poor design no matter the type.