Full details here: Official Google Blog: The evolution of sitelinks: expanded and improved
Think about it logically
Most sitelink results are only triggered when you more or less know what you are looking for eg. "company name" or "product name" or "event"
So the sitelink results, arguably, help to get you to the most important info faster ..
As for the Bing vs Google debate - they're probably talking about the click per position stats. For some bizarre reason Google's higher click is the 2nd position (can't remember where I read that, but I know I saw it somewhere in the last couple of days .. )