I highly doubt a top of the line phone like the Galaxy or the Pixel would have issues with input lag.
If anything, I get annoyed by how long animations on iOS take compared to Android. Everything feels like it's running in slow motion.
Happens in laptops too. Its just silly. Go in the same price range and then make a judgement.
I long for the freedom of android and use iPhones reluctantly only because i really think they are a good value at almost any price point.
Same with LG, Sony and others. The only smooth Android I have ever tried was Huawei's and I am reluctant to buy Chinese telco hardware.
You can compare iphone and android performance benchmarks here [0] and here [1].
Apple devices still come out ahead of top of the range models from other manufacturers.
Yes I know benchmarks can be gamed and don't mean everything, but there is still a performance difference between top of the line Android models today, vs not only top of the line iPhones, but also iPhones from a couple of years back.
0: https://browser.geekbench.com/ios-benchmarks 1: https://browser.geekbench.com/android-benchmarks