CDT, of course you know the group:P And I'm a CDTmember!!! I have build in CDT2011 for the first time because of the age-limit of 16. See more on the CDT websites.
Its not for sure I will build for CDT2012... Because my parents wants to go on vacation and the only chance is between DDT2012 and CDT2012 (12 days). If I have to choose between these two this year, I will choose for DDT2012. Why? There I made a lot of the projects. In CDT its only building them... + It's a bit annoying that you can't talk with everyone (I cant speak german and some germans cant speak english)