At a meeting of my fabulous anime club, I had a chance to watch SAO and Log Horizon back to back, and frankly Log Hor wins hands down. SAO has better production values, it looks like an anime asking for HD experience. But its characters are not anyone I would like to care about. It's odd... Kirito and Asuna seem like upstanding individuals, in the game anyway. Most bloggers zoomed in on the lead being a Marty Stu, e.g. too disgustingly perfect. Not sure if that is the main problem. The lead in Log Horizon is too good too, but his exploits seem more interesting somehow.

Mind, I came to the above conclusion before seeing how the focus of Log Horizon becomes more about improving the world, a significanly larger scope than SAO's.