Well with nani, i see tricks and flicks that may or may not come off, and every so oftern, he'll have a moment of brilliance that could lead to him scoring or providing an assist. Nani has moments of brilliance, in the middle of a bunch of tricks and flicks that may, or may not come of.
But with bale, its always steam rolling past the defender and either putting the ball into a dangerous area, or shooting and giving the keeper something to think about. He almost ALWAYS does this, hence why i believe hes more consistant. Just my opinion.