Carbon low rise 710mm on my Ti456. Feel very planted with them but don't think I'd want anything wider from a twisty tree lined singletrack prespective. Once you are having to change your lines to accomodate your bars things have got a little silly.
The Niner Sir9 I'm sloooooowly building up with an Alfine hub (might be finished just in time to put it away for the summer!) is going to be a long distance bridlway basher so is going to be a little more head down, arse up. Thinking norrower flat bars with bar ends (well, those ergon gc2 things). got to do something to make them look visually different enough to justify owning both!