There are advantages to having multiple subs. One is that it’s easier to integrate a pair of subs into a room than one single sub. Another is that the notion that all bass is mono and omnidirectional is really a myth. There is such a thing as stereo bass. Even if the frequency is low enough to be omni, phase differences in the low frequencies most certainly can result in stereo bass.
Whether it’s worth it to you to have two subs - or not - is another matter.
Whether it’s worth it to you to have two subs - or not - is another matter.