I guess you are referring to matrix.org.
In short, I believe Kontalk aims at simplicity in everyday communications, whereas Matrix is mostly aiming at team collaboration.
In my case, I use matrix through riot.im daily, to follow IRC and matrix channels that I participate in (one of them being #kontalk ). I have also reverted my family to use it for video/audio calls, instead of Skype, for which I have long waited for a decent alternative. It's true that matrix has gained a lot of momentum. Last time I checked, encryption was still not the default option. Registering and connecting is not very simple. I don't think it's very user-friendly for everyday users, but my mom could use it fine after I initially set it up for her and explained the important buttons! It offers many bridges to other networks, which is good. I see it is improving fast and is actively developed.
At the same time, I use kontalk also daily to chat with friends and family. Kontalk is much easier to just download and start to use, as it is probably closer to what people are used to nowadays with messengers. And encryption is always turned on by default.
I keep stating this, but fwiw, I might be among the few that don't see this antagonistically. It is great that nowadays compared to only a few years ago, we have many great solutions in terms of open source, encryption and easy of use in daily communications. Just pick the one that suits your needs best. I would argue that the next major challenge is decentralization and federation.
@OffifialMITX I don't want to edit your post, so please change your title to something more appropriate, like 'How does matrix compare to Kontalk?' or 'What are your thoughts on matrix?'