MSI Afterburner comes with a built-in benchmarking tool known as Kombustor. It hammers GPU to its maximum limits by putting it through a series of stress tests. The main idea behind benchmarking is to find what your graphic card is capable of handling and at what resolution. If you are planning to get into high-end gaming but have no clue how your GPU will react with that much pressure, running benchmark tests would help you determine that. \
Also, if you have set any overclock for your card, benchmarking would be a great way to see if it has made any notable changes to the overall system performance.