For anyone who cares, Here's how the numbers play out.
With standard pvp gear( dual dreams, Treachery, angelics, Arach, magefist, treks, ...) and pre-buff gear.
An average sorc will end up with level 35 lightning mastery and level 49 enchant.
With dual dream build, and 136 dex(the minimum amount necessary to use a pb) on a level 95 char.
You will end up with around 1-50k lightning damage and 20,500 ar
With a visionary helm and the same build, you will end up with
1-22,000 light damage and 23,600 ar
With dual dreams and 132ar/life gcs instead of lightning life gcs, you will end up with
1-32,500 light damage and 28,360 ar
As you can plainly see, using a visionary helm is obviously not the way to go.
Now, using a circlet will give you a slight advantage by allowing you some increased flexibility with the belt or gloves. It will also leave you a bit of fhr short not to mention lower life and mana.