Typing "ass" given the frequency with which we use the word is more likely to result in repetetive strain injury because (a) the double s - can result in microtears in the hand muscles and tendons, and (b) the word comes around more quickly exactly because it's short, resulting in even greater risk of the microtears.
It's well known that most of the greatest guitar players in the history of the world were English, rather than American.... the sole reason for this is that you Yanks crippled yourselves typing "ass" all the time and so have reduced dexterity, while the Poms, who type "arse" (which is much more ergonomically satisfying - type it now, it's like a little left hand practice session for your fretting hand) still have fully functioning fingers and so are capable of much more interesting and complex passages....
Australians, being pragmatic individuals, simply did an analysis on what was in their best interests and voted for "arse".....
All of this is true, I swear....