1) Results are 500x better than competitors like Duck Duck Go.

2) Under EU laws, they'd have to notify you of any major privacy/data changes, so if the System1 connection was an issue we would know about it.
- They have also undergone extensive third party audits, and will probably do so in the future, unlike many other private search engines
- They have published a data flow diagram as well: https://support.startpage.com/index.php?/Knowledgebase/Article/View/1276/0/what-is-the-startpage-privacy-guarding-data-flow

100% recommend StartPage.