Exile
4 Socket Paladin Shields (only)
Vex + Ohm + Ist + Dol
15% Chance To Cast Level 5 Life Tap On Striking
Level 13-16 Defiance Aura When Equipped (varies)
+2 To Offensive Auras (Paladin Only)
+30% Faster Block Rate
Freezes Target
+220-260% Enhanced Defense (varies)
Replenish Life +7
+5% To Maximum Cold Resist
+5% To Maximum Fire Resist
25% Better Chance Of Getting Magic Items
Repairs 1 Durability in 4 Seconds
Phoenix
4 Socket Weapons/Shields
Vex + Vex + Lo + Jah
100% Chance To Cast level 40 Blaze When You Level-up
40% Chance To Cast Level 22 Firestorm On Striking
Level 13 Redemption Aura When Equipped
+350-400% Enhanced Damage (varies)
-28% To Enemy Fire Resistance
+350-400 Defense Vs. Missile (varies)
+50 To Life
+5% To Maximum Lightning Resist
+10% To Maximum Fire Resist
+15-21 Fire Absorb (varies)
Going on stats alone, that's a tough decision. Both shields have their large advantages. If price is the concern though, I'd go with Exile. About the Um'd SS...sorry, not even close to either.