The difference is largely existential: declaring sex is important because it is a choice. Some pronouns shift based on the decision, but such cases are surprisingly few (I welcome corrections from people familiar with the code).
That’s my cue, I guess…
(SPOILERS follow)
Looking at the code, these are dialogue differences based on gender:
“This [clown/chick] given you trouble?”
“There is the perpetrator. Shoot [him/her].”
“Well, [brother/sister], step right up – I don’t care what’s your sickness…”
“Romance: A [woman of mysterious beauty/tall handsome stranger] will soon come into your life…”
Also, in the chase scene, the dealer will punch a male PC in the gut, but merely shove a female PC away.
I see just two other differences: the blind guard and the fat lady each have a special failure response to KISS, but only if you’re of the opposite gender.
Of course, he’s your blind date.
The fat lady is far too distant for your affection.
The puzzle solution about kissing the fat lady’s hand is not gender-specific, but curiously there is a comment in the source indicating that it used to be!
(T ;<FSET? ,BLUE-BOX ,RMUNGBIT>
<WIN-FAT>)>)
In I6 this would be something like:
if (true) ! if (blue-box has punched)
win_fat();
The gender test is commented out, so the action always succeeds, but it seems like it wasn’t conceived that way. In some earlier draft, if you were a female PC, you’d have to use a different action (I think SHAKE or RUB).
Overall, the approach seems rather one-step-forward-one-step-back. The game can’t really think of any gender expression other than “you’re trying to romance someone” (HETERONORMATIVITY ON) or “a male NPC has a dimly chivalrous impulse.”