I would tend to say go with Debian, if that is your aim. While I understand that some of the Ubuntu long-term support releases have stable package bases, I have had nowhere near the same level of comfort with an Ubuntu LTS as I have with Debian stable, especially when boxes are to be migrated to newer releases. With Ubuntu the LTS to LTS hop is often not successful, usually for lack of testing, whereas I've rolled from one Stable release to another many times with no issue. The Debian project works very hard to do regression testing, issuing a new release only when the release is finished. This has proved to be more prudent an approach that that of Ubuntu's, which opts for a hard(ish) 6 month release cycle; a new LTS is release every two years but is a 6 month iteration over the last Ubuntu release plus some influx from Debian Testing.
It could well be that I'm biased--and you should certainly go with what you are comfortable if this is to be a one-man show--but in the pony show that is choosing a server OS, I'd go with Debian every time.
Sure. If you have any problems the Debian mailing lists are excellent, the Ubuntu forums are good and I'm very often polite via email if you have a question that isn't very tightly focused.
