If you force-quit / SIGKILL the app, it won't bother to page as much of its bullshit back into memory as it's terminating it. I'm kind of baffled by the continued presence of graceful shutdown procedures in an age when everyone does recovery on startup anyway.

The problem isn't that the 5400rpm drive is 'slower', but that the average latency is higher (though only by about 1.5x) -- it likely has higher streaming bandwidth simply by virtue of greater areal density.