my vague reaction is that the terms arent so solid, any attempt at communication failed or successful is expressing lots of information and any distilled expression mundane or divine is going to communicate a lot.
i suppose you are talking particularly about writing, so for the arguments sake we can skirt over the problems of talking about Art let alone Great Art as though they refer to a continuous and distinct set of experiences. The last thing i remember reading and really getting into were a couple of books by ann quin last year. a part which stuck with me was where a character is running about a 1950s seaside town in a murderous frenzy and looks up at the hillside in the distance and then perceives the same sensation glancing at the wrinkles on the back of their hand. its this alarming recognition of the way their environment is replicating their extreme mental state and vice versa. you get this sense from drugs sometimes, the porosity between you and your surroundings and the fear that can induce. the way its written in the book you have these two images colliding with each other, but she really nails the voices that capture the mundane grubby seediness of that place at that time.
So altogether its this sort of structural symmetry, the prose and the sense of the surrounding voices vividly mirroring the experience of that hilltop/hand epiphany, which itself is a realisation of that same mirroring process. so rather than expression/communication i think a lot of the things that have really done it for me have that sort of structural symmetry, for want of a better term.
the standard is less is this communicating to anyone, is this expressing something worthwhile but more are the affective levels of the writing reinforcing and intensifying the other effects of reading.