In my view two definitions between opportunities and luck in gambling activities have differences, I personally if it is more guided by luck.

The reason: Opportunities for me are more directed to the probability that I use before I place a bet, meaning I still judge that opportunity as a characteristic or impossible, an analysis or prediction that I do, is not perfect.
But if I am guided by luck for me that is a real gambling, because I am dealing with the game, where I can not be separated from the result of a coincidence or good fortune, Although the opportunities that I believe can win, but the nature of my chances can be wrong, the results of my bet are based on the results of coincidence or good fortune, luck is what I often experience.