I choose .019 cause that is the majority of what is on my sights. I have two Viper Predator Microtunes that each have the top three pins as .019 and the bottom two as .010.
Currently I use .029 but I picked .019 because thats what I will be using hopefully by the end of September if things work out.
I used to use .029 but the newer fibers on the pins make the .019 work really well and I even used .010 last year but I turned my light on the last 10 minutes of hunting.(just in case) I am now using the .019's and they are just about perfect for hunting.
My hunting bows have .019 for 20 and 30 and .010 pins for longer distances. The smallness of .010 really make for pin point accuracy at those distances. The exception is my 82nd, it has .010 pins 20-60.
I have a .29 for the 20, .19 for 30 & 40, and .10 for the 50...however I think I am going to go .19 for 20 & 30, and .10 for 40, 50, 60...
I had used 029 1st pin, the rest 019. for a few years. This year I'm actually going back to all 4 at 029. My eyes ain't what they used to be, and I still manage more than acceptable accuracy for the blue moon frequency that I shoot longer distances.