I like UT3 in its current state, the last big patch resolved a lot of problems and added new content, and there's a good community for it, making all types of superb custom maps and models to play around with. I preferred UT 2004 when UT3 just came out, but right now UT 2004 is almost dead and I only played it in Invasion servers, the server I used to play in lost my character stats due to my prolonged absence, I haven't re-installed it since then. I would say that right now I prefer UT3, but I'm not suddenly saying that UT 2004 was anything bad, I loved it, but it's barely alive now, I think there's more people still playing UT99 than 2004.