There are several reasons why you might lean one way or the other - time to re-build is certainly going to be at the top of the list. But, equally as important, is the technical consideration. There are some courses that are just more likely to be a successful course export/import into Canvas than others. How do you know if your course is a good candidate for copying? In general, the more simple your course is, the better the candidate for copying.
You've attended the Info session, you know Blackboard/Portal is shutting down August 31, so now what? What can you do right now to ensure a smooth migration?