word choice - I would like to use your discretion

At work the other day, I was making something and wanted a senior person's opinion on my creation for Steve.
I said "Hey Steve, can you take a look at my hat, I'd like your discretion."
He said I should've said "...I'd like your opinion."

Now, because it was Steve's job to make the hat, and I was assisting him. I think perhaps I should've said something along the lines of use your discretion. Or may I use your discretion. Something like that. As in, it's his decision whether or not the hat is good enough, gauged through his professional opinion.

This has been eating away at me for days!

Answer

You say in your first sentence that you wanted Steve's opinion, which means that you wanted his judgment on the quality of the hat. But it seems from subsequent sentences that you wanted more than Steve's opinion; you wanted Steve's decision on whether the quality of the work was sufficient, i.e., you wanted his dispositive opinion of your work.

In this context, discretion is the freedom to exercise authority, and the only person who can exercise said authority is the person who holds it. Thus requesting someone else's discretion or using someone else's discretion is inapt. Now, by the very nature of freedom of action, someone with discretionary power may choose to exercise it or refrain from doing so, and you may recognize that fact by saying something like

I understand and expect that you will exercise your discretion to pass judgment on the quality of this hat.

But since you're reporting to Steve, a senior person whose responsibility it is to pass judgment, you hardly need to acknowledge the obvious fact of Steve's discretion. All you need to say is

Is this hat good enough?