Given the options you posted covers a wide range of specs maybe you missed one off of the list and that would be the 830.
As mentioned the 1520 is considered the top of the heap with the 930/Icon as it's smaller brother, only let down by no SD card storage.
The 1320 is a large phone but much lower specs, the 830 is marketed as the "Affordable" flagship, looks like the 930 and is still a very nice phone.
Out and out best I would say is the 1520, followed by the Icon/930, followed by the 830 and then the 1320.
What should you buy, depends very much on what you can afford, if I couldn't have my 1520, I would go for the 930 and if I couldn't have that, I would be very happy to have an 830.
Be aware that the Icon (Pretty much identical to the 930 as sold out side the US) you could run into carrier and update issues.