Hey I rechecked the odds again and MagicDice actually has different multipliers and therefore will win in the end.
In the screenshot you can see that if you choose a 50% win chance you only get payed 1.96 times your bet. So the double betting roulette style isn't working in the long game as they are cutting of 0.04% of every win. So this is how they are making money... ^^

So in this sense: Be smart and don't gamble. The bank/casino always wins. (I am actually quite curious on which legal basis MagicDice is operating as this is basically a online casino for which there are harsh rules in most countries. Like safety of minors or gambling addicts).