There WILL be manga spoilers abound!
I listed both because they are two sides to the same series.
I know there are some other fans here.
I've read the manga of Tsubasa up to the latest, and I like it. Nice thing they are doing with the crossovers, and Sakura and Syaoran being in a new series.
The anime is not bad either.
Kurogane kicks ass by the way.
xxxHOLIC is pretty interesting. Yuuko knows more than we do (story wise), and for the mystery involved.