They are very similar but very different watches.
To make your choice harder....
The only 3 major "downgrades" I see from going PO to SM are:
1) You lose the convenience of the folding clasp
2) You lose the jumping hour hand feature
3) Shorter power reserve
3 "upgrades":
1) Way better bezel action feel
2) Thinner = more comfortable
3) 5-year warranty