Bing has changed from boring to ok. I would choose all of them. Depends, I use Baidu as music search engine.
I'm going to through my hat into the ring here and say my own search engine SeekIt if I didn't have my own. I would use Google, then Yahoo, and last Bing. Maybe ask.com if I'm desperate.
For getting relevant information its google. But if you need for leads and sales - I mean according to marketing its AIm. though they have only 2.5% of the total market share they produce much sales.
Google is the best as when you search for anything on Google you don't get unrelated result you just get what you are looking for.
I am a big fan of Google, so I will say - its Google! I think it so, because of few things: - Very complete, it can find anything. - No ads - just simple and clean. - Super staff - it has a super-awesome staff who takes care of Google 24/7 - Fast updates, they update the search engine every 20 minutes or so. - Works fast. That is probably the most important thing. So, there goes my vote: +1 for Google!