As per robg's usual warning about modifying widgets, it's a good idea to copy the Business widget to your user's Library/Widgets folder first, and then modify that copy. By doing this, you will always have a pristine copy of the original widget should you ever choose to revert to it.
Once you've copied the Business widget to your user's Library/Widgets folder, control-click on it and choose Show Package Contents from the contextual menu. Find the file named PhoneBook.js, and open it in any text editor. We're going to replace line 987 (var mapURL = "http://www.daplus.us/showmap.aspx?";) through line 1009 (mapURL += "&Partner=appleyp";) with this snippet of code.
As you can see commented in the code, changing t=h (hybrid) into either t=m (plain map) or t=k (satellite map) will get you the type of map you desire. I just happen to prefer Google's hybrid maps, hence it's the default.
Save the file, close it, and you're done. Launch Dashboard and open (or reload) the Business widget. After searching for a business listing, clicking on its address will load it in Google Maps. Enjoy and again thanks to phanofwclark!

