I've always enjoyed Linux on X86/X64 - both from a tinkering perspective and as a solution for folk who've asked me to set up a 'no-nonsense' internet computer, the joy of installing a distro that auto senses all hardware, installs drivers, completes all updates and is done usually within half hour is amazing.
PPC not so much, that is definitely under the tinkering for the sake of it guise, as it's a time consuming journey to get any machine close to running properly.
Linux on Intel Macs has it's place I'm sure for those disenfranchised with modern Apple - I myself haven't used a OSX newer than Snow Leopard so I can't speak for how disappointing modern iterations are. However, for design and music, Linux has nothing to remotely compare to what we have available on the Mac and for that reason, my productive machines will always be OSX.
For us who like to tinker as a hobby, Linux is the gift that keeps on giving. I have Linux running on two of my machines- Elementary OS on my Blackbook 4,1 and Debian 8 XFCE on my iBook G4 1.33. I have found that these two systems are the sweet spots for the distros that I chose and am keeping them on those machines. Yes, there are limitations on the PPC install, but I've gotten that install to the point where I no longer want to tinker with it, and it's become one of the machines that I rotate in and out of use regularly. I've installed Linux on pretty much every PowerPC machine with a Radeon that I've owned, and most have too many issues to want to keep the install. My aluminum PB G4 1.5, for instance, was a big disappointment, due to trackpad and video driver issues. No amount of tinkering or research could get these issues to sort out no matter what I did. My DP2.0 G5 HATES Linux with a passion, with stuttering and choppiness while running the X server, but that's probably due to the Radeon 9600 Pro in it. That machine will stay on Leopard, which is very pleasant to use. If you use video playback as one of the benchmarks (and I admit that I do to a certain extent), the latest Leopard Webkit and Quicktime 7.7 makes this a no-brainer, even on my TiBook 867. Your mileage will definitely vary with PowerPC installs.
The Macbook 4,1 install with Elementary OS? Pure bliss. Much faster than ML and much more up-to-date, and as an everyday machine, a joy to use. I still have ML on my other (white) Macbook 4,1 and it gets used here and there, but has various issues that plague it due to the unsupported install (video, etc). I wouldn't mind running Lion, if I could get the machine to boot with the 64-bit kernel (although I admit I never tried with the 3,1 or 4,1 machines and went straight into the unsupported ML install). I'd have to put my recommendation in for Linux or even Windows 7/10 (with the spying services shut off and an extensive hosts file) on the plastic 1,1 to 4,1 Macbooks over OS X, whatever that's worth. Still, I keep my 3,1 and white 4,1 on OS X, just because... well...
All of my other Macs have various flavors of Mac OS/macOS/OS X on them, and they're upgraded and configured for the maximum usage experience. My Bondi iMac has a 400mhz G4 processor (compliments of
@dosdude1) and is a lot of fun to mess with, just to see how far I can push it (compliments of
@AphoticD and HIS tweaks). It plays 3gp video via the View script/mplayer nicely, and with 512mb of RAM and in 16-bit color with shadows turned off, it's pretty speedy as a general-use machine. I'll probably follow his lead and drop it back to Puma, as I haven't spent much time with it except "back in the day". Same with my now-repaired Wallstreet.
We've gone wayyy off-topic now...
