Paru was at one point a rewrite of yay in Rust, and has since continued development as a pseudo parallel fork. It's good. Dunno if it's worth switching, you'd have to see if there's any specific features you might happen to want, but they're both fine
I have decided against Aura because it splits the commands for AUR from the standard repos. With paru I can upgrade both by running just paru. In the end, that's all I mostly do with an aur helper.
Honestly, from a day to day standpoint, by my experience of using both, there's little practical difference between, for example, yay, and paru — it mostly just ends up coming down to subjective, nitpicky meta things about the program itself.
Up until this post, I hadn't heard of Aura, but, after briefly looking at its repo, it appears that it's effectively the same as yay and paru [1.2]; what it tries to do differently is it tries to ensure that there are translations of it (I'm guessing its output) in other languages [1.1.1]. One thing that I'm knee-jerk not super fond of is that it utilizes its own centralized metadata server [1.1.2], though I admit that I haven't thought about that a great deal, so perhaps there are some aspects that about it that I'm missing, or perhaps misunderstanding, or perhaps there's a different way to view it.
[...] From the beginning, Aura has been built with multiple-language support in mind [...]
Section: "Independence".
Aura has its own [...] Metadata Server called the Faur. The Faur in particular helps reduce traffic to the main AUR server and allows us to provide unique package lookup schemes not otherwise available.
Section: "What is Aura?".
Aura is a package manager for Arch Linux. Its original purpose was in supplementing Pacman to support the building of AUR packages [...].