With the rest, lets make a little test. Lately I've been using a program called syncplay: https://syncplay.pl/
On Arch, you can find 3 different versions of it in the AUR: syncplay (latest stable, 1.6.3 at the time of writing), syncplay-git and syncplay-server-git https://aur.archlinux.org/packages/?O=0&K=syncplay
I haven't found an online form to search packages on Solus, but after booting an ISO I can see it is there! https://u.teknik.io/EQOck.png (although a bit outdated, 1.5.2 from a year ago)
Debian, nothing: https://packages.debian.org/search?keywords=syncplay&searcho...
Fedora, no luck: https://apps.fedoraproject.org/packages/s/syncplay
Tumbleweed, nothing: https://software.opensuse.org/search?utf8=%E2%9C%93&baseproj...
Of course, this is a stupid small test. But it is so easy to create and share arch packages, and the user base is so large, that it is almost never the case that what I need doesn't have a build script already, or that the packaged version is too old. And when it does happen, and there is no build script, it is very easy to make one and share it with the world. Or when I really need the bleeding edge for a certain application, I can look for -git packages. I know that on debian checkinstall can help you avoid an /usr/local unpackaged mess, but I have no idea how I'd share that with others.
In short, yes, the ideas between all of these distros are pretty similar, but as far as package availability goes Arch tends to win due to low barrier of entry for packages, and user base size. Its install process is shit, but thankfully I've only needed to do it a couple times.
Oh, and it probably wins on documentation as well. The Arch wiki is just huge.
Which of these is missing from say Solus, Debian Rawhide, or OpenSuse Tumbleweed, not to mention the various Antergos like distros. The differences between distros past the base install really is smaller than people realize, and often people pick distros based on misguided assumptions.