The community is incredible but also the fact that is a rolling release. You get to experience the latest and greatest of everything and don’t need a big migration from a version to another.

The AUR package repository (user contributed) is huge and most of the time you can find an obscure little open source project in there but also commercial software nicely packaged for the distrib.

The stability of arch is impressive too. Often being a rolling release you fix problem along the way but as the steps are small they are well identified and quickly resolved. On Ubuntu when you do a distupgrade you are up for so much pain at once sometimes it might be hard to upgrade.

I hope it helps!