system
Given the following post, respond as if you're commenting on Reddit:
human
CMV: The term "Transsexual" makes more sense than "Transgender" for most people

So we're all on the same page, let's define some terms.

Sex - Biological. Male/female with some rare but notable exceptions. Not that I'll be noting them.

Gender - Psychological. How one identifies and feels.

Trans(prefix) - generally used to denote a change or difference

With these in mind, I believe it makes more sense for someone whose gender identity is different than their biological sex, and who potentially would like to change their biological sex to match their gender, to be called transsexual. It's their sex that they want to change (generally), not their gender.

I know there are people who would rather change their gender to match their sex, but I'm pretty confident that they are a small minority compared to the rest of the trans community.

CMV!
gpt
Since sex refers to biological traits, in order for someone to be transsexual they'd have to have undergone gender reassignment surgery to acquire the biological traits of the sex that they weren't born as.  Transgender people are just people who psychologically identify as the other gender, not necessarily someone who has had the surgery or who will have the surgery.  So while all transsexual people were likely transgender, not all transgender people will be transsexual so it's more all-encompassing to use "transgender".