Aaaaaahhh...this was hard for me to decide, because like felinedacat said, it seems to me like they're both aimed
at different audiences. I mean, Tsubasa RC features the main characters of Card Captor Sakura, which was originally
aimed towards younger children. I think CLAMP was hoping to draw in the people who originally loved CCS as children
with Tsubasa RC, which still has the characters that they knew and loved, but in drastically different circumstances and
more mature trials facing them. XXXholic, on the other hand, seems to have darker themes [ie death and evil - an
example being the woman who was a compulsive liar and was eventually consumed by her lies or the woman addicted to the
internet] that might appeal to an older audience...like the ones who follow X. >< But that's just my
opinion.
Personally, I love both manga. Choosing a favorite isn't really an option, but my preference varies from mood to
mood. Even though Tsubasa RC is more lighthearted, it's less funny than XXXholic [maybe to combat the dark
themes?]. But anyway, right now I'm liking Tsubasa RC more [Syaoran and Sakura are my favorite clamp pairing,
soo....] because I just finished reading the latest one again, and that's why I chose it! I’m kinda fickle,
I think. But yes.
I don't really think I made my point clear, but oh well. Thanks for reading! ^-^ *wave*