If there's a difference, it's not because it's packed. You could unpack it and get a bit-identical WAV file out.
If there was any difference, it could only be because you were playing the packed version on different hardware, or with different software.
Although, come to think of it, I suppose a player program might have some sort of quirk whereby the extra processing power required to unpack on the fly interfered with its audio output somehow. Or maybe audible interference from the PC's circuitry could be marginally worse if it was unpacking. Although in the latter case, you'd have a similar problem if you were downloading porn in the background, or whatever.