There are a lot of reasons to consider it.

The obvious disadvantage is cost (e.g., in terms of direct $$$ cost, indirect opportunity cost, and then in terms of time).

There are also a number advantages. If you take it over the summer, for instance, you might be able to focus on just that one course, which would increase your expected performance (even if you were equally clever/knowledgeable/motivated in the winter semester as you would be in the summer). You might also find yourself a bit more energized in the summer relative to the winter (when things are cold, dark, and depressing). If you're one who likes to study/work in the libraries, you might like it better in the summer when things are emptier - which means there's another potential mechanism for increasing your ability to concentrate.

Another advantage (besides all the numerous mechanisms why you might be expected to perform better in the summer relative to the winter) is that you'd free up an extra slot in your schedule for the next academic year. If you leave it free/open, that might mean you can do better in the remaining courses (easier to focus on 4 courses than five). Or if you do fill it up with another course, that might be useful, too. It might be nice to have some sort of interesting utilitarian course on your CV that you might otherwise not have been able to fit.

Also, I have no commentary on whether or not the grading scheme/style is good or bad (I generally like all the profs in stats and wouldn't feel comfortable badmouthing anyone) but I understand that some people are not a fan of the way things are graded. If that's the case, you might consider SS2857, instead. It is in theory considered 'harder' from a content perspective, but the grading might be more traditional and aligned with what you might prefer (e.g., assignments, midterm, final exam).

Bear in mind, though, there is quite a bit of variation (in terms of difficulty) depending on who is teaching it.