Well, Zaka offer Very good res, good smite dmg when upg, it has Nice + skills(= more dmg), Good block(=more life), Stats(Again= more life), 1 open socket and 20% more ar. Only 1 of this mods are useless for a Smiter!. and that is the Added ar. So Upg Zaka give best smite dmg, best life, best res..
Exile offer: Best def (only good vs: barbs, non smite melee palas, melee assas, and melee druids.), a little max res ( but that sux if you dont even have the res), Life tap (life tap is like, "When life tap trigger i win!!" "well then you got 15% chance to win?").. Then Exile can have More dmg than Upg Zaka, But then You wont have a Res exile... and if you have res exile Zaka give better res + dmg anyway...
So for Smite duells the only Mods that make anydifference at all is: Life Tap, 2 offenciv auras 7 replace life. Cus in Smite vs smite duells def dont have any efect...
Zaka in smite duells this mods that are useful: Skills, stats, better block (you cant block smite, but since your dex is lower you have more life), and 1 open socket ( can be used for like everything..)
Also another thing, Grief give so much dmg that most Smite duells Ends in very Few hits: Means Life Tap have even lower chance to be casted.. With life tap being at the minimum of use, exile is a shield with 2 offenciv auras + 7 replace life in a smite duel..
Edit: Now some1 might come and say: "Exile can have 65%ed as auto mode on the shield, that will give more dmg than Zaka!" Well The open Socket in Zaka can be used for a 40%ed+9 str/dex jewel, giving Zaka even better stats and only 15% less ed.~
~Shadow (Upg. Zaka>Exile)