It really is very confusing. The main difference is the warranty. The CH version includes an extended 10-year warranty from Tamron. Whereas the import version only promises the statutory 2-year warranty.

According to research, there were opinions that there are differences in manufacturing. However, this is a myth. Both lenses were tested in a direct comparison and gave the same results.

You simply pay more for the extended warranty upgrade, which I think is fine. It's to my advantage in case I want to sell the lens again in the next few years.

Hope this answer helps you.