An interesting disovery when running the RT-5100 test case is that doubling the amount of text in Text.content will cause the pure FX version to run roughly half as fast. Doing the same for the versions using Swing JTextArea has no effect on framerate.

So I'm lead to believe that the Text node always lays out its entire contents, even if only a small portion of it will end up on screen. This would explain the large disparity between Swing & FX performance.

See notes in RT-5100 on how to run the test.