Another vote for Debian or Ubuntu. I've been happy with both. Debian is more stable, but if you rely on a recent package (say if you keep your software in git), you then have build or install your own or rely on backports or other unofficial packages. Ubuntu Server is more up-to-date. (It goes without saying that your Ubuntu Server installation shouldn't have any X packages installed, and, by default, does not.)

With respect to Red Hat based distributions, I have always had more luck with apt and Debian packages than RPMs. It probably comes down to familiarity, so YMMV.