Instead of debating, these are the actual results. Clearly, your choice will depend on how much data you want to copy.
byte[] copy performance test
10,000,000 iterations 40b array.copyOfRange: 135ms systems.arraycopy: 141ms
10,000,000 iterations 1000b array.copyOfRange: 1861ms systems.arraycopy: 2211ms
10,000,000 iterations 4000b array.copyOfRange: 6315ms systems.arraycopy: 5251ms
1,000,000 iterations 100,000b array.copyOfRange: 15,198ms systems.arraycopy: 14783ms
