If you exclude the duplicated architecture packages in the Ubuntu repos and include the community-maintained packages, Arch has more packages new packages seem to commonly available within 24 hours of an upstream release.
For example, I use some utilities based on "rofi". A search for Ubuntu packages containing "rofi-" contains just no results, but a search for Arch packages returns about 50 results.
https://packages.ubuntu.com/search?suite=groovy§ion=all&...
https://aur.archlinux.org/packages/?O=0&SeB=n&K=rofi-&outdat...
AUR packages look easier to maintain than PPAs, so I'm more likely to get get involved with packaging something on Arch then I was on Ubuntu.