I have used both; it's not really a question of image quality between the two, but more of image presentation. The IP B&W 2.0 film (at least, SX-70 version because it's the only variety I've shot) is a very contrasty film vs the FP-3000B reveals much smoother tonal transitions (more akin to Polaroid Type 52 material if you've ever seen that.) For example, under the extreme sunlight conditions of the desert southwest (USA) I won't shoot the IP film, but won't hesitate with the Fuji film. On the flip side, under low contrast conditions the IP film can sing! I'm not saying the Fuji film is no good for low contrast scenes, just different than the IP film.
Hope this helps.