An exchange rate that is higher is usually more beneficial since this will allow you to obtain more Singaporean Dollars to use on your travel. A high exchange rate allows you to get more when you are currently in a foreign country and exchanging your local currency with SGD.
On the other hand, a low exchange rate is good if you are already home after your trip and exchanging your spare SGD back into your own currency.
Having a low exchange rate means that your local currency has a value that is greater than SGD, which means that you will get more.