It's not a pedal.
It's just a smaller non rackmount version of the Palmer PDI-03, Although it seems like it doesn't have a dummy load built into it. With the rackmount version you can connect just your head and have a DI output for silent recording. But this one doesn't have that.
What benefits? Options really, do you waste time trying to get the perfect mic position, or just hook this up and your set? Or you can mic the can and use this and then blend them in the mix.
It can help in a live situation where you have phase issues caused between multiple mics and monitors all over the place.
It's a shame that it doesn't have a dummy load like the full sized PDI-03, because then you can't record your amp straight into your interface through the PDI-03.
The new compact version makes sense if you've recently went from a city sized rig, to 4 small amps.
Palmer makes great stuff.