Bind search engine is not bad of searching some one at Internet but If you discussed about traffic then only Google can create 90% traffic at your website and Bing or MSN can give 4 % contribution as traffic point of view.
I would recommend optimizing for Google first and then once you feel that you've done the easy stuff, move to Bing optimizations. The good news is that most of the time your optimizations will apply to both engines.
Bing is one of the search engine that is in the market. Bing is one of the most common search engine used, but if you compare it to the some other search engine then its not as good as Google. If you are looking to increase the traffic on to the site then the best one is to do for Google search engine. By dong some of the things like directory submission in Google and writing blog , articles and many more by which your site rank can be increased.