Brian Leiter's recent poll about views on academic presses that publish in law is finished. While I'm usually (in fact up to this poll, always) suspicious of internet polls, this one is useful for a couple of reasons. First, hey, it's on academic presses, so there aren't going to be a lot of people voting for political reasons. Second, I think the audience who voted are likely to be pretty knowledgeable on this narrow topic.
At some point we should think about correcting for the number of titles published by each press as well. HUP, OUP, and CUP have long law lists--streching back in OUP's case to Blackstone's Commentaries (no, I don't mean the modern edition published by the University of Chicago Press--with fabulous introductions, by the way). YUP's law list is much shorter, but is very distinguished.