You should probably take into account if you can afford to get this B- or C+. If your transcript is littered with C's, you might wanna take that W, but then again would that really be helping you? Take the W only if you feel your circumstances will allow you to retake and get the highest grade possible. As stated above, I'd probably just take the B- or C+ and do well in another class to offset it gpa wise. You've obviously calculated that there is a way to get it done, so handle that 👍