The clothing is just a facade, what really counts is how you act. As such, going fully suited is the best policy, but feel free to customize it a bit.. a slightly informal tie, a quirky jacket, perhaps. You need to look like you've made an effort.

Once you're in and they get a good first impression, then lead with your personality. If you're an interesting person but you don't get the job because you're dressed too formally, you clearly didn't use your personality.. because while first impressions can be made by dress, the impression made ten minutes into an interview should have been driven 99% by the PERSONALITY of the interviewee.

Use the suit to get the first impression, use your personality for the rest.