Neither. Both Solus Budgie and Ubuntu Budgie 22.04 LTS are superb implementations of the Budgie DE. I have used both extensively (Solus Budgie since 2017 and Ubuntu Budgie since April), and both work extremely well for my use case, which is desktop computing without need for complex enterprise management or complex network management tools.
The differences between the Budgie DE implementations are insignificant (the Solus Budgie default theme/layout is almost identical to the Ubuntu Budgie "Traditional Budgie" theme/layout), although (1) Ubuntu Budgie offers a wider variety of themes and layouts than does Solus Budgie , (2) in my opinion, the main menu is slightly better organized in Ubuntu Budgie than in Solus Budgie, and (3) Ubuntu Budgie offers a "browser ballot" as part of the "Welcome" experience that allows users to select a browser from among 8-10 choices.
Both Solus Budgie and Ubuntu Budgie are supported by strong teams and are contributors to the BuddiesOfBudgie project, so we can expect both to continue to stay in the mainstream of Budgie development over time.
The difference between the two is at the OS-layer, the Ubuntu OS layer versus the Solus OS layer. The differences between the two OS layers are well known and frequently discussed. I need not go into those differences for the purposes of this discussion.