i tryed both,
and my opinion is that the L-500 has got a very balanced yet ballsy sound overall, and a very thick and dry tone. it's also very versatile.
the EMG81 is a bit more midrangy and very trebly, with less bass and more presence, but too harsh for my tastes. i dont like it.
well, not easy to get them compared since one of them is passive and one is active, but the L-500 is more organic, juicy and meaty, while the EMG is more crispy, glassy and "artificial".
if you're looking for Nuno's tone, then get rid of the EMG.
my 0.0001 cents.