Why is Java2D faster on the (slow) integrated GPU compared to a fast dedicated GPU?

Question

Why is Java2D faster on the (slow) integrated GPU compared to a fast dedicated GPU?

I am trying to optimize application performance by switching from Java2D to OpenGL (LWJGL). I wrote myself some guidelines to see the difference in performance between the two and was pleased with the result at the beginning. However, when I ran my tests on another machine, the result was quite shocking to me.

This is a benchmark:

public static void main(String[] args) throws InterruptedException {
    //create window
    JFrame frame = new JFrame();
    frame.setSize(1000, 1000);
    frame.setLocation(0, 0);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //add drawable component
    frame.add(new JComponent() {
        protected void paintComponent(Graphics graphics) {
            Graphics2D g = (Graphics2D) graphics;
            g.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
            g.setFont(g.getFont().deriveFont(24f));

            long start = System.nanoTime();
            for(int i=0;i<500;i++){
                g.drawString("This is a test string - This is a test string - This is a test string",10, 20+i*2);
            }
            long end = System.nanoTime();
            long nsDuration = (end-start);

            System.out.println("DrawString takes: "+(nsDuration/1_000_000)+" ms");
    }});
    frame.setVisible(true);

    boolean t=true;
    while(t){
        frame.repaint();
        Thread.sleep(1000);
    }
}