If you are going to trust BoxCryptor you can as well trust BTSync directly.
Of course I'd rather not have to trust either, especially with encryption. Is there an open source equivalent to BoxCryptor?
Note that EncFS "leaks" quite a bit of metadata - you might have problems explaining yourself if you've got files called blockbuster-movie.mpg or kiddie-porn.jpg - in certain configurations those filenames will be exposed (I think BoxCryptor always exposes filenames/directory-structure in the free version).