I have mostly bounced between Ubuntu and Linux Mint for 2 years+ (3 years+ by November). I'm not sure I'd use the term favorite, though--it's just that for a period the Ubuntu based systems seemed the best choice for me and my circumstances. That said, at this point, I have little inclination to move on. However, I was happy with other distros in the past. I happily used Mageia for a long time. My first long lasting distro was SuSE (10 years ago...wow, can it be that long? :lol. I also liked Fedora in the past, but didn't have good enough hardware (read: fast enough--I was using a computer well past the sell-by date). Plain Debian allowed me to keep one old computer running longer than any sane person would try. I also have a warm place in my heart for Mandrake (which became Mandriva, and is the ancestor of Mageia). It was the first distro I really seriously played with. I had issues with the version of Mandrake I used (10?). But the overall experience was positive enough that I saw future in playing with Linux.
In my own one-dimensional point of view fedora is more comfortable than the ubuntu that i tried only because of the different desktops (GNOME vs ... something else for ubuntu). I like the right-click-open-in-terminal thing
I started when I was like ten with mandrake. I went to a store and got the boxed set along with the book. I was able to install it and use it with ease. I ended up using red hat, then moved over to Suse. I wanted to go back to red hat but they started making it commercial only, so I was using fedora for a short while... Then went back to Suse. One of my servers does run centos, although I don't consider it a computer I use. It's just a server. Ubuntu is great with support and updates, but I don't know... I enjoy Suse. I ended up buying a MacBook Pro so I'm using OS X mainly now... But it's in the shop under a repair now.
Keep in mind I'm an über-n00b whose still afraid of the command line. I like Tails and Kali because of the potential. Do I have any clue how to use it? Hell no, but when I do, it'll be fun. Plus, what better way to learn than to try?
I really like Xubuntu, it's lightweight and works nice. Plus it has Ubuntu's/Debian's massive software library.
Since my post above, I started trying Lubuntu, although it's not a "pure" install. (I took existing Ubuntu, and added the Lubuntu desktop.) Not 100% in love; however, it does seem zippier than I'm used to, which is a huge plus given that I hold onto technology well past the sell-by date.
I'm using Ubuntu Mate. I did some googling and it seemed like the best fit for my somewhat old laptop, though I ended up using LXDE instead of whatever it was this came with.
On my server I've got ArchLinux (formerly had Debian). I like it a lot now, I think Arch is the ideal server operating system and it's very well documented. Debian was nice too, though. On notebook I've got Ubuntu. On my desktop computer Win8
I started with Mandrake back in the days when it was the best distro available. I was happy with it for a long time until it got completely broken around the time of KDE 4.1. Then I moved to (k)Ubuntu and I am still there. I also use RHEL extensively, but only as a user, I don't administer those systems at all, I just run some things on them. For some time I also had a home server that had Ubuntu Server running on it. It was an awesome device until the hardware failed, then I just moved the HDDs to a cheap Synology unit. For traveling and for home use I have a 13" MBP, which is an okay machine for that purpose. To answer your question, my two favorite distros are Ubuntu and RH because that's what I'm used to and that's what most software and hardware manufacturers support the best.
