For the SMP midsize/PO debate, here's a pic:
I wore the midsize SMP for years with a 6.5" wrist and thought it fit just about right. I gave it to a sibling after I got a 42mm PO. The PO was initially, I thought, gigantically too big in comparison. It grew on me gradually, the more I tried on larger diameter watches. However, I still like the size of a vintage Calatrava or Reverso Duo--I can't conceptualize wearing anything bigger than 42mm.
edit: I like the suggestion of the 36mm Explorer I. Much more classic and hardy of a watch. Cartier and water are like oil and water in my head.