Xmarks has the advantage of syncing to IE and Safari as well as Firefox. It also has the advantage of a website which you can access from public computers in order to view your bookmarks. Plus, having tried Weave and having used Xmarks since it was Foxmarks, it seems to me to be a much more polished product although Weave's newest release (16 Nov. 2009) is said to have improved things immensely

I find Xmarks' "bloat" can be useful but you are allowed to opt out of it. The Google integration flags sites that are frequently bookmarked in their database. This is covered by their privacy policy: "Unless you opt out, we anonymize, aggregate, and analyze the bookmarks of our users in order to provide a range of Search and Discovery services like Smarter Search, Suggested Tags, and Top Sites."

If you prefer Weave, I don't have a problem with that. But you don't need to attack the competition with baseless complaints.