I don't use either so I don't really care. I just don't expect a consumer service with subpar UI to win market share solely on technical merits.
That makes sense for unfunded projects because most developers are not good designers, and designers don't have a culture of contributing to open source, but for a project that pays (some of) its developers, it's their choice how much to pay developers vs designers vs managers, and they are responsible for the way in which they allocate their limited resources.
I recently had to move my open source project's chat from Gitter to Discord, not because we like Discord or "don't care about open source" but because everyone is so damn tired of Gitter's terrible UX that it became the overriding concern.
Matrix bought Gitter two years ago, and I kept waiting, hoping that they would improve it, but they did literally nothing to it except connect it to Matrix within a couple months – and even that doesn't work well, with Matrix users still unable to respond in threads.
I assume there is a good reason for that. I'm not here to judge, only to point out that this "good reason", whether it's lack of funding or priorities or whatever – won't change anytime soon, so I won't be holding my breath anymore.
We spelt out the good reason in the original blog post: https://matrix.org/blog/2020/09/30/welcoming-gitter-to-matri...
> However: in the medium/long term, it’s simply not going to be efficient for the combined Element/Gitter team to split our efforts maintaining two high-profile Matrix clients. Our plan is instead to merge Gitter’s features into Element (or next generations of Element) itself and then - if and only if Element has achieved parity with Gitter based on the above list - we expect to upgrade the deployment on gitter.im to a Gitter-customised version of Element. The inevitable side-effect is that we’ll be adding new features to Element rather than Gitter going forwards.
We’re almost at the point of being able to switch Gitter over to being a branded Element.