Dropbox FAQ:
Metadata and resource forks
Avoid syncing files that use metadata (or resource forks), including Mac aliases or Windows shortcuts. These types of files typically only work on the operating systems they were created on.
SpiderOak FAQ:
Does SpiderOak keep and restore Mac OS X resource forks, finder color labels, spotlight comments? Owners, permissions, timestamps?
SpiderOak retains Unix/Mac file and folder attributes structures, including uid, gid (ownership), permissions, ctime, and mtime. SpiderOak also retains and restores the contents of Mac OS X resource forks.
Like most backup systems, SpiderOak does not store the atime (last access time) of a file.
Also, SpiderOak does not store Finder colors, or spotlight comments. We will be adding support for these in the future.
Per Matthew Guay in a reply to comments on his Dropbox vs SpiderOak: File Sync Battle article.
the vast number of iOS apps that work with Dropbox make it almost impossible to leave Dropbox behind.
I haven't tested SpiderOak yet due to that (hopefully temporary) limitation.
Another comment there from Daniel @ SpiderOak:
Dropbox is targeted @ novice users while we @ spideroak are much more aimed at advanced users with real security and customization needs.
I submitted a question to SpiderOak re file/folder name issues a la Dropbox's FAQ. EF addresses this issue with this file renaming script.