.019 is a great all purpose size. 010 is really for 3D/target shooters, doesn’t really collect enough light for low light conditions. And .029 is too large for good accuracy at shots past 40 imo.
I have four HHA sights one with a 19 and the other three with 10 size. The 19 can be so bright that you cant hardly see your target with the sun out, I use the 10 pins to hunt, they are brighter than any hunting pin out there in my opinion. Two of my sights have th e sun shade on them , if you buy one try to get it with the sun shade, makes a real difference. I have never had any problems shooting the 10 pins at the very end of any hunts, much brighter than any other sights I have tried. The 10 size allows you to pick a smaller spot to shoot at.