Steps to reproduce:

1. Open attached project
2. Disable VSync in Quality Settings
3. Change graphics API for Mac Standalone to Metal
4. Build 'Elements Preview' scene (Assets/Low Poly Strategy Prototyper/Assets Preview Scene)
5. Run the built game (Fantastic, 1440 x 900)
6. Take a note of the FPS of the player (should be displayed at the top left corner of the screen)
7. Change graphics API for Mac Standalone to OpenGLCore and repeat steps 4-6
8. Compare the FPS in both builds, notice how Metal build runs significantly slower

My results:

Fantastic, 1440 x 900 (on AMD gpu):
Metal: ~125 FPS
GLCore: ~200 FPS

Fantastic, 2880 x 1800 (on AMD gpu):
Metal: 34-40 FPS
GLCore: 55-60 FPS

Fantastic, 2880 x 1800 (on Intel gpu):
Metal: 7-12 FPS
GLCore: 15-25 FPS