if you prefer a chronograph or not. I actually use my chronograph from time to time at work, so it comes in handy. The 320/329 obviously doesn't have that function. I guess small seconds dial could help, but it isn't quite the same, is it?
Price wise, the Omega may be a little cheaper than the 320 and definitely cheaper than the 329. They charge more for the bracelet for the 329 - but that is still less than if you buy the bracelet later. Costs like $2500! I have put the Omega on a strap and it looks good, but the choice of straps comes nowhere near the variety for the PAM.
Size is something to keep in mind. The Omega will be a little smaller - though it's almost the same weight as the PAM 320 - less than the 329 though. The Omega I wore daily for three years and it has kept wonderful time, has been my "beater" if you will, and one couldn't tell by looking at it. It hasn't changed an iota in three years! But I have never seen one in the wild either. I think the 320 would be more common. If you want something few people have, I would go with the Omega. Oh and there is the black dial and white dial. I went white dial and all my WIS friends agree that was the best choice. In fact, as cluttered the dial looks, it is quite easy to read. Of course, compared to the 320, that is a different story! The 320 is a super clean dial. Very nice!
Hope this helps.