| Never did a direct A/B, but I've owned both. To me, the Prunes was a odd sounding fuzz that was pretty nasal with knobs that allowed you to pinch the sound or make it more fuzz-like. I really didn't like it.
The noise-box (a fuzz / oscillator / filter ) had more sonic variety and less of a pinched sound. In a world of infinate cash, I would still own it, but at the time it wasn't that useful for me (and my guitarist HATED it), so I sold it off to resist temptation to annoy him. I would buy one again if the right deal came along (band broke up).
As always, your milage may vary. | 
