No question about it, take the W. While it may look not so great, it will not impact your GPA. Where as a C will not look so great AND it will impact your GPA ( for the worse). This maybe different if your transcript had some W's on it already, but for it to be your first, you NEED to take the W.
I know it must suck having to withdraw after a ton of hard work, but sometimes you have to bite the bullet and do whats best for your future. Good luck.