If we are going to talk about it in terms of risk, it is almost the same since you are putting your money in risk. Investing is full of risk since you do not know what will happen to your money whether it goes up or down. This is not really the same but people is talking about it in terms of risk only. Do not take it as it is and full understand it first.
This answers your question. They all think that there are a lot of differences but I think there are common things that can affect the outcome like luck, and for the difference betting will rather give a quick income if you bet, but in investing there is a long term goal where you will want to hold until you double your initial investment. Think not of them as comparison rather they are more like analogy.