[AreaOfEffect]

It isn't really a fair comparison. It's a gold heavy unit versus a resource heavy unit. It's important to remember that resource isn't a limitless supply. It also means that the units naturally have different strengths.

Heavy infantry are ideal against units that use light weapons, such as short swords and spears. They generally have shields and so they fare well against missile fire. Heavy infantry are made to beat light calvary, so the comparison is even less fair.

Light calvary generally come with bows, combined with their fast movement they become ideal for hit and run tactics. As mentioned before, they are great for raiding provinces.

Dominions is often a rock-paper-scissor game. This would become more apparent when you include barbarians into the equation. Barbarians often beat heavy infantry because they can overcome their protection and the infantry don't have missiles. Light calvary often beats barbarians cause they have bows and their higher defense works better then protection.

So please stop comparing.