TOAST, large objects, and ACIDity

Hi all,

I want to use postgres to store data and large files, typically audio
files from 100ko to 20Mo. For those files, I just need to store et
retrieve them, in an ACID way. (I don't need search, or substring, or
others functionnalities)
I saw postgres offers at least 2 method : bytea column with TOAST, or
large objects API.

I wonder what are the differences of the 2 methods.
* I found that large objects need a vacuum after delete to really
release place. That may be handled by a trigger or automatic vaccum, is
it right ?
* Large objects are used via a special API available in libpq C client
library.
* I really care keeping my transaction fully ACID. Documentation on
large objects doesn't explicitly say if lo_import an lo_export (and
other primitives) are fully ACID. Some ideas ?
* I going to bench insertion and read with this 2 methods.

other advices are wellcome.

thanks

Benoit