I am considering purchasing Hartco Urethane Parquet tiles to glue down on concrete. I seem to have to decide whether to get builder grade at half the price. What is the difference? Is it the thickness of wood, lacquer quality...? Is it worth spending double for the wear and tear that the higher quality will take? Is there a difference in how it looks?

I didn't think Hartco was still in business. Their pre-finished parquets have been around 25+ yrs. Laid a lot of it years ago. Now, a "cabin" grade or builder grade are seconds. These are pieces culled out during manufacturing for flaws. The flaws are usually visual only and include poor coloring, knots, bad milling, etc. They are usable but also take longer to install, due to the poor milling of some. I never liked using cabin grade products and unless they can be had for next to nothing in cost, I do not think the low cost out weighs defects.