in the end you cant go wrong with both! $$ will probably make the choice for you.
It might bring you to another price range for the 320 and Joey said it right

... brings you
312|..............$...|233 (that much closer). and the bang for the buck from a 320 to a 233 is even greater!
To me it seems the 320 is the middle child in the 1950's models. I know there's a GMT function added, but with the used prices of the 233 coming down to a attractive level the gap is tightening.