uma das respostas está no fim do texto:  Fast decay mode has the side effect of high current ripple. Remember the current is swinging considerably more than on slow decay mode. This poses a few unwanted problems such as EMI magnitude increasing (larger current peaks are of course gives a stronger radiation) and more audible noise, depending on the current chopping frequency.

Mas se mais alguém quiser contribuir, eu também gostaria de saber mais detalhes!

andré