It actually differs per owners niche. If you're more with the financial markets it's better to manage a trading business or an exchange rather than running a casino that you don't like and not your niche.

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.