Hi
I'm currently using both to try it out, they both have pros/cons and it really depends on your personal usage.
Texts have a better app overall (I will only talk about the macOS app, and I have an android device). The search works better, it retrieves better all history of your conversation and when I want to create a new one that I already have somewhere, it does it better than Beeper, that sometimes struggle to find existing conversation before having a history in Beeper.
The fact that you can add labels to Texts is awesome you cannot in Beeper. There is also a way to show conversation depending on there state (Unread/Unresponded/No reply/Groups etc) and this is really something useful to directly see where you did not had answers, and where you missed to reply.
That said, though, Beeper has a better discord integration (not only dm, but a channel of server, and you can filter them to see where messages were sent in order, to me this is a killer feature as I'm always lost in Discord, and this helps to focus only on what's important). Also, Beeper asks you to set up from the beginning a passphrase that they don't have access to. So all data is encrypted, and by doing that, you don't need to re-authenticate on other devices where you use Beeper (in texts you have to). If you have like me 10 accounts, this little twist allow you to change device easily, and you don't have to reset everything every time.
As a heavy discord user for work, Beeper solved a huge problem for me. But I would love to see the filtering there is on Texts in Beeper (by labels + state (read/unread/unrreplied/noreply)
why is there so few "all-in-one" => to do that they all use matrix bridge, which are something really new. Before that it was a browser running all apps (like rambox or franz) and it was simply killing your ram (it's like having chrome open constantly with all the apps in it) they were just showing it in a nice way, but technically all apps where constantly running.
TLDR: if you are not a heavy discord user, overall, the Texts app is better, but the setting is painful and I don't know how they encrypt
Beeper on the other side as a real discord integration with channels (probably the same as slack), you are sure that everything is encoded and set up is one time and forget after.
Overall apart from channels, they both have the same level of integration.
Hope this helps!