One of the key highlights of Bing's user interface is a new annotated photo that appears on its homepage each day. Not only does it provide feel-good feeling (and good information), it also includes links to interesting searches related to the photo.
This source shows that Google's use of Doodles in 2009 is expected to be the highest ever in its history (assuming its collection is exhaustive).
Update (13-Feb-10): Google's Doodle has become larger, taking it closer to Bing.
Google.co.za homepage (South Africa) on February 13, 2010