I think a lot of people's Linux distro preferences boil down to which distro they started with. Ignoring my very first disastrous attempt at Linux with Slackware, I eventually settled on the old Red Hat free version, which today is what became Fedora. As such, Ubuntu and Debian seem foreign to me, and I run Fedora on all my servers (including GPF). (But I'd never run Rawhide on a production server; I'm not that stupid.) Fedora has served me well ever since, so I haven't seen the need to go with anything else.
As for yum vs. dnf vs. apt-get: I have no experience with the latter, but so far I haven't noticed any difference between yum and dnf. I'm hoping there's some significant changes under the hood to warrant the change, because if it was just a "we're getting tired of calling it yum, so let's rename it" kind of thing, that's pretty annoying. If I have any complaint about Fedora, it's how things seem to change arbitrarily between one version and the next. I keep a series of notes whenever I rebuild a server to prevent myself from making the same mistakes again and again, but that document always requires tweaking because Fedora restructured a folder or renamed an essential tool in the new version. My hosting provider has a nifty scripted deployment feature that I'd love to take advantage of, but I can't, because the only time I roll out a new box is when I'm upgrading the OS, and it changes too much between versions for me to script it.