I am in a slightly odd (though not unique) position in which I used to have the iPhone 4 until 6s before switching to a Samsung S7 Edge. I also have an iPad Pro 2017 for work.
I like iOS, and it was unquestionably superior to Android until about 3 years ago (in my humble opinion). Since then however, Android has surged ahead.
Many people will say it’s not quite as secure (which is true) but I would say that Google Pixel and Samsung Galaxy phones are pretty much on par in terms of security due to their Titan M and Samsung Knox security chips/software.
I much prefer the freedoms, appearance and extra features that Android offers over iOS, despite it coming at a (slight) cost in ease of navigation...customisation is one area where iOS noticeably lags behind.
To clear things up, Google DOES use your data BUT you can control what data they receive and share more easily than most people think. On the flip side, Apple doesn’t ask for much of your data, which results in inferior helpful apps (ahem Siri)...whilst Google may demand more but in return the services are much more useful in helping you along your daily routines.
Speed wise, both are fast and fluid (high end models). I still prefer using my iPad for work over an Android tablet..but I have to say, the Files app is a complete mess. Hope Apple fixes that and adds more computer-like features with iPad OS.