In 357Mag you get very good performance out of the 4.68" tube.
The only reason I might go longer is if it was a hunting gun - and esp. if I was considering sending the 9mm cylinder to Gary Reeder to be reamed out to 356GNR (41Magnum shell necked down to .357). This is a large-frame gun so Gary would do it gladly - plus sell you dies and reloading data. The gun could still be switched to 357Mag any time you want, and you don't even need to send Gary the gun, just the cylinder.
But as a plinker and/or defense gun against man or beast, I'd stay with the gunfighter length. As one example: I once shot a bowling ball with a NewVaq357 of that length and DoubleTap's hottest 125gr load - close to the heat of a Buffalo Bore or Underwood load. I blew that bowling ball in half, sent fist-sized pieces of the concrete core back past my feet (and I was about 25 feet back). The fact that it was a nice dead center shot helped but the ammo performance was damned impressive.
