Performance beast ... maybe within the confines of the walled garden, fast as only against other iPhones. The rather distinctly old tech mechanical home button is like a governor on an industrial engine. It limits how fast you can go, no matter who you are, or how fast the cpu/et al is. You still have to wait for the button which can only travel up and down so fast.
For a truly fast experience just buy yourself one of the leading Android Flagship phones, with just one exception. Copy Cat Samsung chose an Apple like mechanical home button, therefore they're just as slow as iPhones.
Despite all of Apples bragging and hype, one can only surmise they cling to the old school button because at a glance its one way to quickly identify the smartphone someone else is holding as an Apple. The average Apple customer is clueless and buys the brand no matter how it's configured.