I'm in accounting, so my perception might not be perfect for finance, but I would choose Booth and it's not close. A big part of that perception is because Chicago controls JAR, which is a top 3 journal in accounting. I believe Oxford controls RFS. If there is some really useful connection with LBS there it might help sway things, but I doubt it. Chicago has the current editor of JF and people on boards at every good journal.
I'm also American, so there could be some bias there. I think most people would say Chicago.