Benefits of headless rendering

Years ago I read that headless rendering is much faster for animations than rendering from the GUI. Tonight I decided to test it out since I’m getting to a point where I’ll need to do at least one 3+ minute animation per week.

When I rendered the first frame from the GUI, the scene consisting of a simple cube on a 50 x 50 plane moving along a path, it took a little over a minute at 256 samples.

I started it rendering from the command prompt and it’s taking a little over 4 minutes per frame, four times longer than rendering from the GUI. Is there something I’m missing?

Even though I set it to use four threads it doesn’t have the same impact on other programs as running with the GUI so I see how it could be beneficial when I need to work on something else while an animation is rendering, but did I miss something that would lead to the speed increase I read about or did that go out with the internal rendering engine?