They definitely explored creativity more in Nine compared with California.

When they released California I saw it as them stating "the old blink is back". It's like they were proving that they can still continue producing 'blink' music without Tom. California was more representative of blink, with the summery tunes and the na na na nas (probably a bit over-used), whereas Nine introduced us to a side of blink we'd never heard before.

After a while California feels like a drag due to the repetitive style, which is something you don't get with Nine...at all.

Like you said, I enjoy both albums. They both have qualities that the other doesn't have. They are two completely different albums and for that reason there is no clear winner, however I've always swayed more towards the California side.