For me the difference would be: if the write past the array has been detected before it happens (via a range check) it would be a regular error which which can be handled, while a panic would be "oops somebody else has written past the end of the array" (e.g. a hitting a canary check), which should abort immediately because at that point it's no longer guaranteed that any recovery code would even work or just make things worse (e.g. trying to flush data from memory back to disk, but that data might have been corrupted too).