lots of customization options for both the interface and your profile, but more important to most people is being able to use emojis/stickers from your subscribed servers everywhere on the platform. This might seem petty, but there's no other software that I regularly use that requires me to pay in order to for example, change the theme of the interface.

edit: that does not include the stuff that I knew I was paying for and was on purpose paying for, like better stream quality and larger upload size and extra shit for my server.