I guess it depends on what your threat model is, if the NSA are after you as a person of interest, full disk encryption is the least of your problems, you should probably just stick to a one time pad and abacus.
If you want to keep a potential thief from accessing your documents if your laptop should get stolen, any of the closed source full disk encryption packages will do.
If you're really worried about it, just double up, use full disk encryption from one of the vendors then encrypt the sensitive files with an open source tool as well, the more layers you add the harder it becomes to compromise.
Fyi, Mac has full disk encryption built in: system preferences > system & security > file vault. (Just don't backup the keys with apple)