Structure / blocks order on a shopping cart page

I'm working on a shopping cart page. I designed it following the idea of a progression (order > delivery > payment) so already entered informations are summarized on the left, and new informations are entered on the right part (left is past, right is next in left to right languages) (figure A).

I saw on various websites the opposite structure (figure B) (fill new informations on the left part, summarized informations on the right).

Which structure do you think is best ?

Figure A

Figure B