When I was looking on Bing and Google, I seem to be finding more up to date satellite views on Google than on Bing. What I can recall seeing on Google a couple years back, I was seeing on Bing, when I knew that the Google map was newer, and showing things like a newly installed road, or at my house my dune buggy in one shot, and on Bing the old van I drove before buying my dune buggy.
I also see my sister's old van, not her new car in the Bing pictures, that must have been taken in 2007 or 2008, while the Google maps in her area show a new shopping center, not found on Bing.
Also while looking up a house on Bing, I saw bare ground, while the google shot showed the house built in 2009. This was in Gresham Oregon.
ALso if you know of new road construction in a area, look at both Google and Bing, and see what site shows the most current construction.
Fred.