Sentence two does not follow from sentence one. If data on one drive is corrupt, deleted etc then the mirror or raid array is also corrupt, deleted etc.
Your active system is your data. It is not a matter of one being better than the other. Not really sure what you are saying.
I actually think we probably agree, but...
Having a mirror or RAID array does not impact the data corruption or human error component. When data is transient, it can be corrupted. When the medium allows access and editing, the data can be lost to numerous events including human error. As the data is written out from a camera sensor to the buffer, it can be corrupted. It does not matter if I've writing to a flash card, hard drive, 2 hard drives, a RAID array, etc. Hence, any argument you have made concerning a RAID array, is also valid in every other data transition scenario. It is true, the a specific implementation of a RAID array may in fact, be more vulnerable than some other implementation. This is why "Moving" files from one place to another on computer system/network is really a copy and delete operation and not a true move. The original is not destroyed until the copy is validated (or should be).
Just the fact that data is on a medium that is re-writable, put it at risk from some threats. Assume a Writable and a Rewritable DVD containing the same data. The data on the rewritable DVD is at more risk precisely because it is rewritable. However, they both share other risks of the same type, if not the same magnitude. Things like disc warping or surface imperfections.