Why would you choose Microsoft Ad Center other than AdWords?

Most would agree Adwords is the better option, but there are some benefits to using microsoft ad center.

People who use Bing/MSN Search, are usually the guys who are new to computers and that is the first search engine they usually come across, it's built into IE (their first web browser).

That means they are much more gullible/easier to market ads against. Placing ads on keywords on Bing will let you get much more traffic than on Gogle.
The sponsored/paid ads section comes before the actual search results and for a newcomer it is very hard to distinguish the two apart without experience on the Net.

People who use google, on the other hand are usually experienced with the web and won't click the sponsored ads when they are looking for something, as it is not the most relevant.