As an international person, if the items were valuable, I would want you to use the more expensive option.
The USPS tracking numbers do keep a great track on where items go (one of mine once got detoured from VA to Bangladesh and then Dubai and then finally to the UK and to me, and I know that thanks to that free tracking option from the USPS. But the item didn't go missing, so I have no idea if it would help in terms of insurance...I waited it out because I knew what country it was in, even if it wasn't the right one.
But yeah, with something valuable, it's better to take the higher option with the best cover for you and your buyer. Maybe talk to them about it too, but it's generally better to spend a little more on shipping than lose it all later on because of a postage issue.