I believe, it depends on the user how much knowledge he has when it comes to forex or crypto trading. Both have the risks of losing your funds, but it is your acquired knowledge and skills that will aid you in battling those risks. But the simple difference of these 2 was posted by mk4, so the OP has basic understanding about these 2 kinds of trading. And just to elaborate further for example in crypto trading, if you are long enough in this market, you can easily spot possible ponzi scheme, pump and dump coin or scam coin. So your trading will be influenced on how deep you know a specific coin.
We can apply to both of them with the same strategies and trading in general whether it was crypto or fiat related (like forex) knowledge and skill are absolutely required. And they all are risky.
Dump and pump can be experienced by both of them but in regards to Ponzi schemes and scam coins, these only exist in crypto trading IMO. In fact, this is one reason why many traders are preferred to use forex trading as likely to avoid losses because of choosing the wrong coins.
But the advantage in crypto trading is to have a lot of choices, unlike Forex. If we are new in trading, better to start Forex first, and gain some experience before moving to crypto.