In my experience, companies care more about your competency than what you look like.
I would say dress comfortable.
You want to present yourself as confident, intelligent and competent. In my opinion, the best way to do this is to wear nice, but comfortable clothing. Not something that distracts from the conversation, but nice enough that you present yourself well.
I don't know any developers that would hire you based on what you wore to the interview.
Think harder about the questions that they will ask you, and less about what you're going to wear :D