I think 'wri mem' is older than copy 'run start config'.
Am I wrong?
Write mem is older.
As of ~11.1 Cisco started with the Copy Running-config Startup-config"
I did some classes on 11.3 and the instructor said that "write mem" would be gone by the time 12.0 came out.
Pix OS still (as of 6.4) uses "write mem" ... I don't know about the 7.x series.