I think it would be worthwhile finding out what the pros and cons are when comparing Bing maps and Google maps...in my opinion Bing maps work just fine (although both have small errors of accuracy and Bing Maps are of low resolution in areas outside of highly populated regions like Iraq, Iran, Saudi Arabia) however, Google as a brand has captivated the market for world coverage of aerial imagery and alot of qustions on this forum as ask how can I use it Google Maps in ArcMap?
But does Google really have 'better' imagery? or system?
It all depends on where you are needing imagery. I've seen areas where Google is better than Bing. Also depends on what you're using it for in ArcGIS. As for me, I am having to digitize in building outlines from the imagery, and I've found Google has provided the most current building structures on their imagery as opposed to Bing and ESRI imagery. Again, it all depends on where you are and what you're doing with it.