Bing Maps is better!
Living in Central Florida, I'm finding Bing Maps to be more accurate and overall, a better mapping app. We've had some major road construction in recent years and I find Bing Maps usually has more updated maps and routing before Google.
For instance, when I need to go somewhere, I'll often map it in both Bing and Google and probably 98% of the time, Bing will have either the better or more accurate route. I think a lot of it has to do with Microsoft's partnership with Nokia, since Bing Maps now uses a lot of Nokia's superior mapping technology and more international countries. I also use Bing Maps on my mobile device and it works great!
PS - I've used it when traveling and had the local natives comment on how accurate it is and how it often chooses the same routes they themselves have discovered from living there for a long time. That says a lot to me!