The 500+ changes a year at Google, most of which were not requested by users, is taking its toll on their performance as is the incessant push to make people sign up to G+ when they aren't looking for a second social network. Will current Google leadership wake up in time to knock it off? Bings not waiting to find out and I STRONGLY suspect the new bing changes(adding social to the right of results) will even the playing field out further.
I'm happy with Bing at 30% though I'd prefer a 50/50 split, or perhaps even a 60/40 split in Bings favor if the 500+ yearly changes don't slow down in the name of stability. Almost every week your site does something odd an unexplained in Google results, not so with Bing.