I think not a lot. An equatorial mount has the advantage that cancelling the rotation of the earth is very simple (just a constant rate rotation around one axis

I think not a lot. An equatorial mount has the advantage that cancelling the rotation of the earth is very simple (just a constant rate rotation around one axis), so tracking inertial stars is easier, but the main movement of the ISS is due to its orbit, it’s just overlaid with the rotation of the earth. But if you have to track both axes anyways, having the rotation of the earth cancelled for free doesn’t help a lot.