xwiki vs twiki

Hi, all XWiki users, I know this is a tough question.... Anyone has experience in using TWiki and willing to point out why would anyone choose XWiki over TWiki? I know both are pretty good, both are open source, both have many supporters, both can do almost the same things, but for someone new, what are the reasons to consider to choose XWiki? For it is written in JAVA? for the user group? for the future direction? for the access control? Wei-hsing ps. Anyone plan to attend Wikimania in Taiwan this summer? to learn from the MediaWiki or WikiMedia? (I know Vincent is, right?)