YOU my friend have sorted through all the hyperbole and come up with the RIGHT conclusion! The 6.5" partial shroud barrel is probably THE ideal of all the .500 models!
It POINTS the best of all....balances far better than the 8 3/8ths barrel, and does NOT deliver anything close to the sonic wave impulse to the ears as does the models with the removable compensator.
It weighs very little more than the 4" model, and IF S&W has done their job right it will deliver greater velocity than the short barrel (though my 4" model shoots almost 100 fps FASTER than my 6.5" model).
The main advantage to the 6.5" is how naturally it comes onto target...maybe not meaningful when shooting flapping paper, but VERY important when shooting at a head the size of a transmission, covered with fur, and topped off with finger-length teeth!