Warcraft III - does it matter which level a Hero is in regards to what the most powerful item is?

I made a few videos about which item is the best when it comes to pure combat power. But does it matter which level a Hero is when you want to determine which item is the most powerful? In this test I picked the Archmage and tested this Hero with the three "+6 on a single attribute" items from level 1 to level 10.
As usual the base damage of the Archmages has been set to their average to avoid random number effects.
In all tests the blue Archmages have a single Robe of the Magi, the green ones have a single set of Boots of Quel'Thalas and the maroon ones have the Belt of Giant Strength.

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