Well said Duke . . . I'd just like to add that at the frequencies covered by most side/rear/bottom mounted woofers, the wavelengths are long enough where the driver is essentialy a monopole (omnidirectional), so which direction they're "firing" per se is inconsequential . . .
But changing on which side the woofer or port is mounted (all else remaining equal) does usually change the proximity of the woofer to room boundries, and changes the distance between the right and left speakers a little bit as well. So for mirror-image pairs of speakers with woofers mounted on the sides, you typically get a difference in the bass response when you swap the left and right speakers with each other.
And there can also be a certain amount of unintended noise (surround or spider flexing, tinsel lead slap, grille resonance, port chuff, cabinet resonances, etc.) that can be much higher in frequency and quite directional, which will have different levels of audibility when the woofers are facing different directions.
But changing on which side the woofer or port is mounted (all else remaining equal) does usually change the proximity of the woofer to room boundries, and changes the distance between the right and left speakers a little bit as well. So for mirror-image pairs of speakers with woofers mounted on the sides, you typically get a difference in the bass response when you swap the left and right speakers with each other.
And there can also be a certain amount of unintended noise (surround or spider flexing, tinsel lead slap, grille resonance, port chuff, cabinet resonances, etc.) that can be much higher in frequency and quite directional, which will have different levels of audibility when the woofers are facing different directions.