It is a bit like asking which car to buy.... Personally - Debian, If you are looking for a bit more automation a-la Windows, go for the *ubuntu flavors.
I am running Debian "Lenny", which is the release candidate for the next stable build. It's been rock-solid, fast and reliable for me. The easiest way to install it if you have a wired broadband connection is to download the latest net install build for your architecture: Index of /cdimage/daily-builds/daily/arch-latest And of course, if you need help, there are several of us here who run Deb ourselves. Just start a new thread and we'll be glad to help.
