Seriously, I like the 5-1/2" gun for all-round use, but think the "fixed sight" 6-1/2" one has the best "look". Viewed from a distance with no scale reference, I think it looks just like a 7-1/2" Colt SAA.
Now, now,, you can only get a 7-1/2" Single-Six in the Hunter model,,,! No fair showing that beat-up old shootin' iron. You should just send it to NC for a few years of test firing!
Have 'em in 5 1/2", 7 1/2" and 9 1/2" but I kinda like a in the middle length of 6 1/2". they have a better balance for me with the smaller frame and visually are more appealing to me.
I prefer the 9-1/2" & the 6-1/2" personally because I am always hunting or target shooting. The same on my semi-auto Mk II's I use alot the 6-7/8" or the 10" I have the "Great Eight" but it is NIB & I never have shot it.
I have a 4 -5/8" new model and 6 1/2" old model. I like them both, but if I had to choose one, I would pick the 6 1/2". For me, the 6 1/2" seems a bit more accurate.