Check it out, the ES stats of the weapos are:
AS: 57a 133d 278s
CG: 131a 74d 462s
and for comparison, a 45a 90d -25s SJF/CJF/JF enchants to 74a 119d 265s and a 102d goes to 85a 136d 323s. 51a shurk goes to 75a 24d 323s
All these numbers are enchant ONLY. My recommendation is either use the CG or trade for a better CJF/JF. Although you gain more def from the AS, the gain in attack and skill (imo) from the CG outweigh the lack of def. The best AS in the game fully enchanted is worse then a 102d CJF/SJF, so don't bother trying to get a better AS. If you were to trade for a better lefty and assuming you've got the back roll, I would suggest for a CJF over 108d or a shurk in the upper 60's
As a side note, I collect AS and I am missing a 104d from my collection, if you ever decide to sell yours, lemme know
EDIT: I voted CG =P