Is it better to run a linux distro on an old mac or go for an older OSX version?
Well you can just have an up to date Linux system, that can be as bloated or bloatless as you want. It may take away some battery life and cause some thermal issues because of how Apple designs their products though, but you can probably fix that with some fiddling.
Really if you have the know-how, you can configure Linux any way you want.