Dual subwoofers (like the SB3000) can provide some major advantages, such as more even bass distribution throughout the room, better sound quality and reduced distortion due to their two-driver configuration. This makes them an ideal choice for larger rooms and more challenging audio setups.
On the other hand, a single PB1000 can still provide plenty of powerful bass for typical home theater setups – typically at a lower cost than two SB3000's. Additionally, it's important to point out that the PB1000 has a larger driver that can produce deeper bass tones than its counterpart.
At the end of the day, deciding between these two options ultimately depends on your desired outcome and budget constraints. It's essential to consider the specific characteristics of your room and audio setup before making a decision that best suits your needs.