What benefit could Persians have derived form conquering Greece in the Persian War?

They used superior naval tactics and destroyed the Persian navy, which threatened the Greek cities and also protected their supply line.

When sea supply was lost, the Persians had to send half their army home, which evened the land forces up.

The Greeks also operated on broken ground which negated the advantage of the superior Persian cavalry.

Their infantry had armour, which gave them the edge over the unarmoured Persian infantry.