benefits of having less fan? reduced noise, and a bit more battery life (and possibly a warmer lap
my hp netbook has a very noisy fan, that always seems to be running 100%, but doesn't run that hot (at stock speeds).
if you disable 'fan always on', it will still turn itself on when necessary, and slow itself down during cool periods.
i suppose it all depends just how loud your fan is - would it bother people sat near you in a library, for example?
reading your post again, it seems that yours isn't a problem