Those three do seem like the popular ones amongst the tinkerers.
Could I ask what your favorite things about Gentoo are?
For me, with Arch, it's how up-to-date the repos are and how it doesn't make me compile everything myself. Should something not be available in the repos, chances are I can still compile it myself and build a package using AUR.
A large part of it is just that it's "home" after finding it at the right time in my skill curve - probably could've been Arch as well.
The Arch wiki might be a bit better and we all benefit from it to some extent, the Gentoo wiki is also good and honestly I don't use either that much anymore.
The great differentiator is portage. I never run into "maintainer built the package without xyz support" - sometimes I'll run into "stupid user disabled xyz support when installing" but that's just a config change and easier to accept since I'm the stupid user. In theory they might've missed adding a USE flag for that feature and I'd have to overlay my own ebuild or live without it. Custom source patching is built in and package versions can be (un)blocked via package.mask/.accept_keywords.
Version 4.3 broke something? package.mask: =pkg-category/pkgname-4.3 to downgrade to 4.2 and still automatically get 4.4 when that shows up. Mask >=4.3 instead and nothing will change (but eventually dependencies might force you to fix it, of course).
Compilation is pretty fast on a modern computer. Significantly slower than binary packages sure but it's mostly with browsers and maybe qemu/compilers that you really feel it (and several of those do have binary packages, e.g. www-client/firefox-bin, dev-lang/rust-bin). On my old laptop this turned into an excuse to experiment with distcc and nfs for speedups (Core2Duo with 4GiB RAM is a bit weak for encrypted ZFS + compiling gcc, and also it's fun).
Compilation times is still the strongest con but having compilation as a first-class citizen is what enables most of it and the big stuff you just run in the background.
(For the unaware, do note that "compiling myself" means "emerge pkgname" or "emerge -auvDNU @world" and includes dependency tracking, not "./configure && make" and manually hunting things down.)
Could I ask what your favorite things about Gentoo are?
For me, with Arch, it's how up-to-date the repos are and how it doesn't make me compile everything myself. Should something not be available in the repos, chances are I can still compile it myself and build a package using AUR.
Another thing I like is the excellent wiki.