I don’t think you need a driver at all, because the PSR-S975 is “class-compliant” and isn’t supposed to require a driver. But if you want to install a driver (which can help with some computer systems), you want to use the first one— the Yamaha USB-MIDI driver. The other driver— the Steinberg USB driver— is for models that have a built-in USB audio interface, which I don’t think the PSR-S975 has. (It’s not the same thing as being able to record audio onto a USB drive.)