Eva Amsen at the Expression Patterns blog asked if people preferred giving talks or posters. The winner, by about a three to one margin, was a talk. This is about the ratio that I saw the last time this came up.
I have not seen a discussion of which format people prefer as an audience member, though. I think a poll may be in order... check the right hand side of the blog.
Updated, 26 November 2014: Fixed link rot. Hat tip to Morton Ann Gernsbacher.
Poster or talk?
Should your first presentation be a poster?
Poster versus talk, May 2010 edition