The two processors are much worse, not the same level, a11 is 4 years earlier than a15, 4 years in the current society is already several generations of products in terms of mobile phones, it can be said that can not be compared, but, as an Apple mobile phone can not say can not be used, because Apple in addition to the processor is very good, its ios system is second to none. Taken together, these two things mean Apple phones will last longer than Android phones.
The process is different.
The biggest difference between the Apple a11 processor and the a15 processor is that the two processes are different. The a11 processor uses TSMC's 10nm process and was released in 2017 for the iphone8 series. The a15 chip uses TSMC's 5-nanometer process, which was released in 2021 and is equipped with the iphone13 series products.