Budgie is independently developed now, but until quite recently and for the entirety of its existence was tied to Solus.
Personally I prefer Solus Budgie but as stated by everyone else it's a matter of personal preference.
It comes down to whether you want to be able to use .deb files or not.
I prefer Solus' stability over Ubuntu's user base. I find Solus to have everything I need. Ubuntu, on the other hand, has repos full of outdated and unmaintained software.
I have broken every single installation of Ubuntu anything eventually. However I have run the same installation of Solus since 2019 (without reinstalling) and have never run into an issue which I was not able to fix, no matter the severity.
In closing.. Solus Budgie is my preferred version of the Desktop Environment because I prefer Solus. If I -had- to use another version of Budgie, I would switch to Manjaro Budgie. The Budgie applets are a bit more customizable and I like Manjaro.
Just a matter of personal preference.
Btw.. from what I understand Fedora is coming out with a version of Budgie called 'Fudgie'. Fedora has the best implementation of Gnome out there and I would be interested to see what Budgie is like on that distro.