Are there any other differences between the H4-3D and the H3-3D, besides:
        - H4-3D supports GoPro HERO4, while H3-3D supports GoPro HERO3
        - H4-3D supports adjustable tilt speed, while (apparently??) the H3-3D does not (tho the tilt-speed is barely adjustable by "slowly" moving the tilt toggle switch or dial, depending which flavor you have)

Any other differences?

BTW, I have mounted a GoPro HERO4 onto my H3-3D and it seemed to work fine.  Meaning, the USB port works to broadcast the video to my First-Person View (FPV) screen mounted on my Controller.

My H3-3D works fine with my Hero4.