Thanks, Christina!
It actually is possible to combine the two using just one capture. However, you are right that it is not easy in the sense that doing so would be very time-consuming. The time-consuming part would be making the sherry appear when using the dark background with the same color and vibrancy as it appears when using the bright background.
Notice that the color of the sherry in the first image is not vibrant, which is my primary objection to that image. The sherry is actually acting as a lens that displays the black background material. It's doing that in the image using the white background material, which is exactly the same size and position as the dark black background material. The difference is that the bright background shows the color of the liquid whereas the dark background disguises it.
Alternatively, I could combine two captures, which would actually be less time-consuming. Even so, I like the bright background so much that, for me, it's not worth the time to make such a much more difficult image knowing that I probably wouldn't like it any better and possibly not as much. So, you lose.
