They've very different beasts, the MXR is a vintage, guitar overdrive, whereas the Ibanez is a modern bass distortion.
Basically the MXR is what a I call 'clean' distortion, it's in the tube screamer family where when you click it on, you don't loose the tone of your instrument, you just get more gain.
Whereas the PD-7 has a more pronounced, "hello I've just turned on the pedal" sort of sound, all though this is lessened at low gain settings on the overdrive mode.
I don't think you'll get the same sound from the Ibanez, one of (this is just a guess) fundamentals of the tone is probably the MXR overdrive pushing his Ampeg rig into dirty territory as well.