The sweater version of the bar jacket runs more true to size and also has stretch, but the original bar jacket runs small.
It may be my personal shape (although I think I have a pretty straight body?) but I ended up ordering two sizes larger and also had to get it tailored (the Dior tailor) to let out some seams in the underarms because it was tight but had to remove excess fabric from other areas. The original bar jacket is a really lovely silhouette though, which the sweater one doesn't keep as well. If you're buying in the store, you should definitely have them tailor it to you.
Here's a photo of it on me for reference
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