Both have different markets and target users but I can't say which is more profitable. But let's end it this way that both really are profitable businesses and that's why we see new casinos being built and launched left and right, and the same goes to the newly launched exchanges. Because both of them drive more money to both economies.
We can get a glimpse here (
https://coinmarketcap.com/) it shows over $200 billion in 24-hour trading volume. But since we’re talking about trading as a business, it’s not just limited to crypto trading.
If you do some research, you’ll see that trading and gambling businesses are almost on the same level in terms of potential profit. But for me, personally, I think trading is more profitable because it’s more stable in the long run. The thing is, it’s not ideal for small capitalists.
With gambling, you can actually start a business with way less capital. So it depends on your resources and what kind of risk you're willing to take.