In contrast, Google and Facebook are companies that sell advertising. The value they can offer to publishers and advertisers completely relies on how well they know their users. Their competitive moat involves collection of proprietary data to continuously improve their products. These are clear incentives to be sticky and greedy with your information, but also to keep it private and proprietary for their own sake.
With these incentives in mind, I more readily trust Apple when it says that it will not collect my data compared to data conglomerates, and Apple hasn't done anything to aggressively betray that idea in its history (to my knowledge). Combined with the technical security advantages of iOS, I'm inclined to believe Apple products to be the least-bad option for the security-minded today.