Well, for most small A/C units you can get your own logo/company stamped on the outside, and have the same parts as everyone else on the inside. Have the contractor give you extensive cut-sheets, or tell him no way. You're the engineer, you have the control of what gets installed no matter how many temper-tantrums the contractor throws. If you don't like it find an aspect of it that doesn't meet what you want. If the contractor can't get you the cut-sheets, refuse to OK it. And I like the excuses contractors come up with, be just as creative in your replies.
But if it works, it works. No need to have a knock-down, drag-out fight over something that says AIR-FLOW on the front when all of the components are just as good as what you spec'ed.