I think these are two activities that do not fit into the same category, so it's difficult to do the deeper comparison. Trading is more like an investment, and gamgling is more like a game. From my point of view, trading is a better option because it allows for more stable profit and better control of risks.
Don't forget that there is a portion in gambling that makes it as an investment too. A lot of casino's are offering their gamblers to invest to them by simply depositing into their bankroll. Still trading is better even though there is an offer like that because you are the one who is going to make your own profit with your own trades.
That is quite different from gambling. Investing in a casino is truly is an investment and not gambling. You are not really gambling but investing in the house. The one accepting the bets, the casino or house, will generate profit in the long-run. This is how casinos work. The don't earn from short-run events but as time goes they will win over the gamblers.
What did just I said? I didn't said it is a gambling but I said it is making it also as an investment. Yes, we must not aiming for those short run way of earning which is happening with gambling. And the better way of doing is that you are going to get good profit is simply having sometime to focus more with your trading career.