With the white posts, I would go with the tan for contrast. What will your flooring be? And if you can get the section between the posts and the ceiling to be tan that would be great, so get the contrast there too.

Either would be ok, but I think it would seem more coherent to match the other vertical surface, letting the ceiling be in contrast. That is, tan. :)

If you want a feeling that it's part of the house, use Sand (tan). If you want to feel that it's a room on it's own, put it all white. I prefer all white.

Thank you everyone for your thoughts. So helpful on here to post questions. The floor is the red/gray/bluish slate that was here when I bought the house. I'll be doing red board and batten shutters that match the interior entry door and the sidelights.

I decided on the tan. Thx for the input. Once it's finished and inspected, I'll try to remember to post a photo.