Now I can't see why a cat should have a favourite OS but it seems Dave (our cat) prefers Kubuntu over Windows XP. She (yes Dave is a female cat) has never shown much interest in Windows XP over the years. When I experimented with Kubuntu, on an old PC I had lying about, Dave became very interested in what was happening on the monitor. Maybe it was the compiz fusion desktop that I was working with. I don't know.
I was rather impressed with Kubuntu myself. It was very easy to install and once installed Kubuntu automatically connected to the Internet and the shared files on my home LAN with no configuration required. Kubuntu comes with Open Office installed so straight away you have a very capable home office PC.