Sex vs Gender

From my understanding
Sex = biological. The anatomical make up of your body.

Gender= how you identify. It is a sense of self and determined by you and not society.

Just because a person has the sex of a female does not mean they identify as such.

Now gender roles = social differences between male and female. They are how one's society believes a person of a certain gender should act.

 

In my point of view, "gender" is not really about social differences, it is more about which "sex" your mind would fit better. So most of the time, people try to match their gender and sex. This to attraction labelling purposes doesn't really matter which one you use, but typing this I realise that saying "same sex" makes a little more sense.

Here is an example:
I can same I'm attracted to "the same sex" and this would include cis-men and transexual men.
I can say "the same gender" and this would include cis-men and trans-men who haven't or won't change anything in their bodies.

Technically I fall more into what would describe "same sex" but it doesn't really matter, they are pretty much the same thing. There are also the factors about whether the person is post-op, pre-op and how they fall into the gender roles, romantic attraction, etc. so yeah it doesn't matter

 

Here's how I think of it:

Sex is what you want between someone's legs. Gender is what somebody's identity is. Though I call myself gay, I guess I'm technically bisexual.

Some people need certain parts for a relationship to work out. Personally, I don't care what is between your legs. As long as a person identifies as a man, I could potentially be attracted to him.

So basically, I'm attracted to the male gender, but a man could have a penis or vagina and I couldn't care less.

 

Sex is anatomy; gender is identity.

How to define sexual orientation (by sex or by gender) is up for debate, but I've always found it most prudent to define it by perceived gender (or perceived sex, depending on which you prioritize). Initial attraction forms before you know what's in someone's pants (someone may only like penises, but could easily be attracted to a pre/non-op trans man they didn't know was trans), so basing that off sex would be inaccurate. It also forms before you know how someone identifies (a straight man could be attracted to a non-passing trans man, but that doesn't make him not straight), so basing it off gender is inaccurate. I find that defining sexual attraction based on perceived gender (or sex), while defining desire for certain genitalia as a preference or a dealbreaker (depending on how much it matters to you) makes the most sense.

E.g. I used to ID as only liking girls. I would have been interested in cis women, female-presenting trans women, and non-passing trans men. I would not have been interested in cis men, non-female-presenting trans women, passing trans men, or non-passing trans men who I knew were trans and thought of as a men. I didn't like penises, so I wouldn't have been interested in sleeping with a pre/non-op trans woman, but I was also only about 14 and really wasn't interested in sleeping with anyone, so that wouldn't have been a factor in my relationships. I was a "lesbian" because I was only interested in people I saw as female. Now I ID as bi, and I've found it's more accurate to say that I'm interested in people I perceive as any gender, but still don't particularly like penises, so I wouldn't pursue a sexual relationship with anyone who had one. That doesn't mean I wouldn't still form an attraction to them; it just means I wouldn't sleep with them, regardless of their gender.

 

Sex = physical
Gender = mental

 

You can still care about genitalia. A guy attracted to the same sex would be attracted in cis men and pre/non-op trans women, regardless of how they presented themselves (a lot of trans women would not be comfy with that). A guy attracted to the same gender would be interested in men, cis or trans. It is still possible that he might only want to sleep with someone with a penis.

Again, I find the sex-based model of attraction impractical because you don't know what's in someone's pants when you first experience attraction, but the gender-based model still needs to be able to factor in preference/need for specific genitalia because that is a very real need for many people.