Pacaur seems like the more feature filled AUR helper. It also seems much more active on it’s github project page https://github.com/rmarquis/pacaur compared to yaourt https://github.com/archlinuxfr/yaourt.
The annoying thing about yaourt is those dam confirmation dialogs.
Also Pacaur is written in Python, as opposed to Bash. Which I think is a much more suitable language for a project of this size.
So my advice is go for Pacaur!
A even more feature filled AUR helper seems to be Aura. Though I guess it needs a bit more adoption. It is written using Haskell and supports some very cool features - rollbacks, deleting unneeded cache files and more - this readme page might be useful: https://github.com/aurapm/aura/blob/master/aura/README.md