This could be a very short review. If you're looking for a fuzz/distortion pedal for bass, buy this one. I'll tell you why.
I've played bass without a fuzz/distortion for years. But when I started playing in a rock band, I felt I needed one, so I borrowed my guitar players Turbo RAT. This little thing will create an awesome distorted bass sound, but there's one big problem. It's useless in a live setting, because, like almost all distortion pedals, it sucks out all your low end. Which is never good for a bass player.
In comes the Big Muff Deluxe. It has a blend knob that allows you to control the ratio of dry and wet signal. That means you can decide how much of that original low end bass tone you want to keep in your sound. Combine that with a switchable high- and low pass filter and a gate function, and there's no fuzz/distorted tone you can not create with the Big Muff Deluxe PI.
Like I said, best fuzz pedal you can get for bass.