Bing has a great search engine user interface, but during testing of various search phrases I've found that (despite their commercials) they still haven't got their engine as good Google's. They don't get rid of the spam sites as well, nor do they find the legitimate sites in all the 'weeds'. Google has optimized and refined their search engine for years with the best engineers in the world (arguably, but Google definitely has talent).
So... For now, I'd say stick with Google. You'll notice they're updating their user interface to give it a little flare. If you want that flare, its coming.