According to my research, there is no technical difference between the lenses. CH lenses have a longer CH warranty from the manufacturer, as in this case. You have to register and benefit from a longer warranty than usual. In addition, only CH products take part in cashback campaigns etc. part. Important note:
Tamron Swiss guarantee
10-year Swiss warranty - registration on Tamron CH website - registration deadline: 2 months after date of purchase. The Swiss Guarantee and national cashback campaigns cannot be guaranteed for marketplace suppliers.
CH variant
EU variant