It has been quite a while since I did any hiring or firing, but I always felt that the person who bothered to dress in a suit cared just a little bit more about getting the job. In the actual selection process, I was usually more interested in the person's qualifications rather than in the way they dressed (within reason of course). In the case of a tie among applicants, however, the better dressed would usually get the job.

In business situations involving customers/clients, you always want to dress just a little bit better than they do. Don't overdo it though.

Good luck.

Wes