It completely depends on which jacket and which Birkin. I would jump through a million hoops to get hold of some Chanel jackets, and would absolutely pick any of them over a Birkin, especially an 'ordinary' everyday leather Birkin.
Am not really a Birkin person, either, though -- prefer the Kelly look.
So many opinions thanks for for them all. I think I might get a birkin first then get a Chanel jacket. I might be able to get both. But only one Chanel jacket. Both birkin and the jacket will be preowned. I think it's more worth it that way.