The iPhone XS and XS Max models have collectively outdone their predecessors when it comes to capturing a share of Apple customers in their launch year. They have also exceeded the iPhones 8 and 8 Plus when it comes to gaining this share in the week after their launch. However, the iPhone 7 Plus remains the most popular Apple smartphone.
https://www.notebookcheck.net/iPhone-XS-series-has-outdone-its-predecessors-in-first-week-sales.337046.0.html