If you define performance as apps opening quickly, and moving through home screens smoother, and general responsiveness of the UI, I think Apple does a great job of optimizing iOS7 for their current flaghips.
If you define performance in terms of customizability, multitasking, wider options, etc, iOS has quite the distance to cover (not used iOS 7 yet, though) . There is no denying that Apple makes great hardware, but the software just hasn't demanded much from it, given iOS's limited capabilities. And when it does (think iOS4 on iPhone 3g or iOS 6 on iPod Touch 4), the hardware doesn't cope well - lags and stutters abound.
On my Galaxy S4, on stock Touchwiz, I have observed stutters and lags. On my old Galaxy Nexus, never seen these same things.
I think a better statement to make would be - all devices made by lazy manufacturers (Samsung on the S4) or by manufacturers wanting you to upgrade (Apple) lag, irrespective of OS.