The site www.bing-vs-google.com provides search results from both Bing and Google in a single webpage.
To make it the default browser search in Firefox and Internet Explorer, simply click "add to browser search" on the site's home page.
Changing Chrome's default search is not as simple, but can be done easily.
1. Right-click on the Chrome address bar, then click "Edit search engines..."
2. In the Search Engines pop-up window, click "Add"
3. In the Add Search Engine window, enter the following values, then click OK:
4. Select the "bing-vs-google" entry in the Search Engines listing, then click "Make Default"
Now you can have the benefit of both search engine results.