A big part of it is what package managing system is used and how updates are distributed, and also whether the creators have favoured older more stable code verses the most recent (but less well tested) versions. A less important part is the software that's bundled by default. An important thing to note, is that you can run most features of most distributions on most others, so you should see your choice as a starting point, rather than the destination. It's also quite simple to set up a virtual machine (e.g. via VirtualBox) to have a look at distribution before you perform a real installation. Even a "less" customisable distribution like GNOME will seem much more configurable than Windows or MacOS. It's what I use on my main PC and I have a whole bunch of tweaks and extensions installed.

This video may help you out a little.