Cash is only safe as we keep it. It's entirely dependent on how safely we handle it. Plus, travellers carrying excess of cash in their wallets are very easy targets for thieves abroad. The biggest issue regarding cash is In case of theft of cash, there is no protection for your stolen money. It's as good as gone. Cash is a universally accepted means of payment and it only differs from country to country in the form of different currencies. To carry different currencies as cash and making sure they don't mix up and to pick out the correct currency, all these are hassles that travellers can do without.
Cards have better exchange rates compared to cash. For the same amount of money, you can buy more foreign currency in forex card than as foreign currency in hand. Cards come enabled with chip and pin technology and hence provide more safety features. When you are travelling to many countries, prepaid travel cards allow you to load multiple currencies in them. In case of theft or loss of your card, you can have the card blocked and also transfer the funds to your new replacement card. This replacement card is usually given as a backup along with your forex card kit.