This has been discussed before, and I’ll say again that polished concrete is the way to go. If you’ve ever been in a Home Depot, you’ve seen why they polish their floors. Everything is brighter, and it looks cleaner also.
If you do go with a coated or stained floor go with a really light color and it will lighten up the room. My first coating on the smaller shop was a dark blue urethane that failed right away due to the manufacturer mixing it wrong. That was lucky for me because the manufacturer paid the installing company to diamond grind it all off. The color was pretty but the room was really dark. Would have probably had to double the lights in there to get it back to normal.