nothing like each other. i have and use both but they are nothing alike.
the clapton/guy boost works best with bright pups and the tbx tone control to bring high end back into the tone.
the pup booster is a clean boost and even with the res switch moved it doesnt change the tone the same way. itll add a little bid beef but not like the fender boost. i like the #1 setting on the pup booster with alnico V vintage toned single coils but prefer the 0 with all humbuckers.