Is sexual/physical attraction prejudice in disguise?

However, you're asserting a Cartesian dilemma where none truly exists. You can, with certainty, say that you prefer orange juice because it does have a higher content of citric acid than apple juice. This is observable.

You have a preference based on observable, reasonable qualities of an object.

Sexual attraction can be the basis for "prejudice" or "discrimination," but I wouldn't necessarily call it a prejudice. A bias, certainly, based on both conscious and subconscious desires. I tend to find certain traits in people attractive, some of the I'm conscious of, others I'm probably unaware. Then again, I can't really just decide to find the opposite attractive.

Jam it back in, in the dark.