At what point to people stop recommending Twilight Mithral Chain Shirts? It's a waste of gold. If you need a high AC, then the BSF isn't doing his job right. If you want a high AC, there are better ways to go about it.
You can tack on enchantments.
Lesser Crystal of Arrow Deflection + +1 Mithral Buckler: 5,650 gp, +2 shield bonus to AC (legal Magic Vestment target), +5 untyped bonus to AC vs ranged attacks (including rays)
Lesser Crystal of Screening + +1 Thisledown Shirt: 2,400 gp, +2 armor bonus to AC (legal Magic Vestment target), -5 penalty to incorporeal touch attacks against you
Greater Mage Armor spell: basically free, +6 armor bonus to AC (also effective vs. Incorporeals)
Total: +8 vs. melee, +13 vs. missiles, +11 vs. incorporeal touch, top functionality until dispelled.
vs.
Lesser Crystal of Screening + +1 Twilight Mithril Chain Shirt: 6,350 gp, +5 armor bonus to AC (legal Magic Vestment target)
Masterwork Mithral Buckler: doesn't do anything, but is a target for enhancements.
sometimes Shield spell: basically free, +4 shield bonus to AC
Total: +9 vs. melee, +9 vs. incorporeal touch, not always at top functionality.
I like the top better.