Off the top of my head, I'd say the big disadvantage of boosting volume post is that you boost the entire spectrum (though, I'm sure you could tweak this with some programs). By boosting the entire spectrum, you are increasing your floor noise:
You rig has a floor noise of -60dB, and you record with a max. of -16dB. Later you boost the -16dB to 0.00dB, that also brings your floor noise up to -44dB... Not a big deal on the loud sections, but on the quiet sections, you may hear a little more hiss than usual...
Of course, the main adavantage is that its louder... But louder doesn't mean better sound...
Terry