UbuntuDDE should be more stable. I believe it is still based on the current version of DDE, v15.
The issue with DDE and stability is caused by a few things:
- The DDE development, at least from the outside, appears to be a little chaotic
- They are only targeting and testing against their own base
- They often abandon old version when they are working on the next
The 3rd item is really the biggest issue. It isn't a huge problem for Ubuntu/Debian-based distros because they have a fixed base. In other words, once it works, it should continue to work until the next major version of the distro is released. For Debian and Ubuntu LTS, that is quite some time.
On the other hand, Manjaro/Arch is constantly evolving so the Arch-maintainer has to continuously patch to keep up with Arch. Since Deepin doesn't merge patches in a timely fashion and/or archives old versions altogether, this means managing a manual patch-set that keeps growing as Manjaro/Arch continue to roll forward.
Ultimately, that all results in instability.
To make matters worse, due to the above, the Arch maintainer has to switch to the beta version a couple of months ago which has made things even less stable.
Apparently, there is some talk about the Deepin test team also starting to test on Arch which would be a big step forward if it happens.
Keep in mind, I am totally on the outside of that process. My understanding comes from reading posts and bug reports in a variety of locations.