I have 2.5", 3", and 4" 686's, and would consider a 5", but the 6" feel to muzzle heavy for me, thus I have not, nor want to get one.

As for HD, I personally would not want to use a revolver longer then 4", and much prefer a 3" or less, as someone else above mentioned it is easier to control if they were to get close enough to grab it.

And if you think that could never happen, you feel free to live in your little fantasy world, as for me, I know that anything is possible, including the possibility of someone grabbing the barrel of my revolver.