I recently started using Telegram as my primary messaging application after growing tired of Discord and the shenanigans they continue to pull. I've even gone as far as to move our friends groups chat to Telegram. Most of them were more than willing to jump ship with me and move to Telegram.
There are a few reasons why I've opted for this migration and they all boil down to the following points.
Message Retention Policies
Discord lacks any message retention settings at all. Period. Your DM history lives forever without anyway to clear it (aside from manually deleting every message you've ever sent). Discord servers do have the ability to delete a channel, which in turn removes the messages (at least from end users view), but why should I be forced to delete a channel to clear it's history. You can have a bot delete messages for you via the API, but the rate limit makes this useless in practice.
Telegram, on the other hand, has message retention settings for DMs, group chats, and channels. You can set messages to automatically be deleted after a user defined duration. This duration can be defined anywhere between 1 day and 1 year of message publishing. This allows for a much greater level of control over your chat history.
Pricing
Discord is overpriced for the features you get and those features are mainly cosmetic in nature.
What is with the super reaction "per week" pricing? lmao
Telegram's pricing is much more reasonable for similar if not the same level of cosmetic and non-cosmetic features alike.
Telegram costs $35.99/year if you pay on an annual basis. Compare that to the $99.99 price tags for Discord with their annual discount.
When comparing non-cosmetic features (features that actually provide more functionality), Telegram again takes the cake. With premium you can upload files up to 4GB in size compared to a 500MB limit in Discord.
Yes, Discord does have some nicer conference calling and screen sharing features, but for the use case of a casual group chat, this isn't really that important.
Bloat Features
Discord really leans into some bloat features and they charge you a premium for it. Stickers and super reactions are two examples of these. Yes, Telegram also has stickers and premium emojis packs you can pay for, but again, the price is more in line with what I'd expect for simple cosmetic upgrades. The channel activities in Discord is also something I consder to be bloat and an obviously blatant attempt to try and add value to their overpriced premium offering.
Client Weight
Discord's desktop client has gotten really heavy over time and the app doesn't perform well anymore. Starting the application on my laptop consistently took 10-15 seconds to get running while Telegram took 3-5 seconds. The mobile apps were compariable though and both were fairly snappy. Although Telegram does have a slight edge here as well.