What is better: quality or quantity?

I recently tried playing as Humans on Veteran difficulty. I chose Dugald. And at the first opportunity, I upgraded the archer dwelling. As a result, I had very little ore left, but I got very effective archers. And then I wondered, did I really need those archers to defeat a bunch of pathetic gremlins and others? Therefore, you need to choose something balanced. I generally don't upgrade anyone at the beginning; I focus on fortifications and the Capitol. As soon as I have the Capitol with a castle, I can upgrade the archers and swordsmen (so that the swordsmen can protect the archers with shields when fighting neutrals). However, this only works for Humans. For example, with Orcs, I upgrade all three of the first-level units as soon as possible.