Sorc A:

Main weapon: Destruction staff
Skill Bar: A, B, C, D, E (all sorc spells)

Off weapon: Healing staff
Skill Bar: G, H I, J, K (all healer/control type spells)

Armor: All light armor

Sorc B:

Main weapon: Destruction staff
Skill Bar: A, B, C, D, E (all sorc spells)

Off weapon: Healing staff
Skill Bar: G, H I, J, K (all healer/control type spells)

Armor: All medium armor

Sorc C:

Main weapon: Destruction staff
Skill Bar: A, B, C, D, E (all sorc spells)

Off weapon: Healing staff
Skill Bar: G, H I, J, K (all healer/control type spells)

Armor: All heavy armor

Given these three players, if all else is completely even, as far as skill and situation, etc. Who do you think would have an easier time in ESO in general and why? If you put the heavy armor guy vs the light armor guy in an arena, who do you think would win and why?

There is nowhere near enough information to even begin to effectively speculate.

Irrelevant.

Sorc B would be a weapon focused character and not using staves. You dont build character around Stamina when you dont plan to use it

Sorc C would be a tank focused character, weapon again isnt fitting entirely, hoever build with Pets/Daedric Protection/Conjured Ward might be possible

The most skilled player. The difference between the 3 armor types should be mobility (easier to dodge attacks) vs defense (easier to absorb damage).