if the featureset is not clear enough at first glance
My experience as someone who has barely dabbled in Matrix, tried comparing clients, and knows a lot of people who stick to Discord: a lot of Discord users heavily use custom emotes, voice chat, and screen sharing. It's not even easy to figure out which Matrix clients support each of those features without installing everything and trying it out. There's a clients comparison on matrix.org that mentions Voip but not stickers or video.
For stickers alone:
Element is widely considered the go-to Matrix client but uses a strange integration system for predefined sticker packs instead of the MSC2545 stickers that more closely resemble what users coming from Discord would want.
Cinny seems to have the best support for stickers/emotes but its site doesn't mention them at all. It supports uploading and managing sticker packs at either a channel or user level, provides a nice picker UI to send any picture from those packs as either a large "sticker" or a small inline "emoji", and allows using them for reactions.
FluffyChat mentions stickers on its site and has the second best sticker support, with all of those except reactions and a graphical sticker picker for inline emoji (need to type them as shortcode).
SchildiChat, Nheko, and NeoChat have some sort of limited support for custom stickers/emoji. NeoChat is the only one of those that advertises stickers on its main site. Nheko mentions them in a GitHub readme.
Being able to freely use custom emotes without paying for a Discord Nitro subscription nor server boosts would be a great selling point but it's not something most users would be able to figure out before signing up. The limited client support isn't great; e.g. Fluffy is the only Android client that supports sending custom stickers but some people may dislike the chat bubbles style UI.