If you have the integrated GPU on your intel processor enabled properly and are gaming on the geforce, the quicksync encoder ends up getting you the best overall performance due to the fact that it's running on an otherwise completely unused part of the processor.
Using NVEnc or QuickSync frees up more CPU time for other things you're working on such as your game, and using quicksync instead of nvenc in your setup means that your geforce card is ONLY trying to handle the game and isn't trying to handle rendering the stream as well.