You should really ask for reasons why people recommend or dis-recommend one distro or another. Without arguments such recommendations are rather pointless. Debian isn't bad but I'd think it's best for servers and not so newbie friendly. Also Gentoo is pretty different from all those other distros considering that it's based on source packages, not binary ones. ubuntu is rather an improved version of Debian - it's based exactly on Debian - but meant for desktop users and with more up-to-date packages. It's very odd if someone recommends Debian but tells you to stay away from ubuntu. I suspect political reasons.