Google - just because it's a habit, I suppose. I have tried Bing, and it works as well. But then again, so does Yahoo. For most basic searches, all search engines will generally give a good result. I use google because that is what I've been using for the past 8 or years, and I can't be bothered to change it to Bing.
Plus, Google's interface is simplistic and clean and not cluttered with images and pictures and all that stuff, like it is with Bing.
But no, I have no real reason to use Google over Bing, other than the fact that I've gotten used to Google, and I don't like the name Bing. Really.... Bing? As in "Bing! Your page has been served!"? Is "Bing" supposed to invoke the noise my microwave makes when it finishes warming up a dish of cold pasta? Because that's really what I want to be reminded of when I use a search engine.
On the other hand, Google is meaningless, but sounds like Googolplex which is a big number and gives the impression that the engine can search through a lot of pages quickly. I am aware that Google has not indexed a Googolplex amount of pages (which is more pages than in existence), but I like the science-y sounding name of Google.
Does google keep info? Yes, I've heard that it does. But I'm not searching for "bad" things, so why should I be worried? I have anti-virus software that rids my computer of cookies and I have set up my browser to clean cookies every time I shut it down. So I'm not worried, really. Google cannot use the info against me, and to be honest, why would they? Who am I? I'm a nobody. Google have no reason to come after me, and even if they wanted to, I think they would have a hard a time searching through all that accumulated data to find something out about me.
Maybe in the future I'll use Bing. Maybe. But it would take something pretty major to make me change.