All of the above. Plus, you may find that a song that works very well live unexpectedly just doesn't work the way you want in the studio (for all kinds of reasons), so rethinking during recording may be necessary, and therefore possibly some weeding out. Also, the running order is crucial, I think, to create a mood and an overall 'shape'. The same 12 or 14 pieces may work or not work as an album, depending entirely on their running order.