I think the only reason anyone even wants to compare or place these 2 on the same level will be because of the kind of loss and negativity attached to both. Betting to me has a higher risk level because you do not decide the outcome in any way. Over a thousand circumstances determine if you win or lose. Ponzi is still kind of a bit of your own way. You are able to calculate the risk and either run or stay, something like that. A person into betting might stake a very little money and win so huge an amount.
The only thing that is very common with gambling is that you get greedy, you lose a lot of money. It's why gamblers are always told to gamble with only what they can afford to lose.