You say that you can bring your grade to at least a B-. If you can make a B- in the course, then I think it would be a no brainer to just stick with the course. While I don't have any concrete evidence, if you were to send a Fall semester update, a W might look like "this applicant received interviews and just decided to drop his/her hardest course to have a light semester."
However, if you do not plan to submit a Fall semester update (if you're put on a waitlist for a school, or if you're waiting to hear back from a school, these can help), then it really doesn't matter.
Hope this helps,
Kevin W, MCAT Tutor
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