I like the .019. For today's speed bows that have flatter trajectories at further distances, your pin gaps will be tighter and the .019 fibers help you to achieve that without sacrificing your sight picture.
I have the 7 pin Tru-Glo Extreme and I like it for 3-d and target shooting, but for hunting I will stick with a 3 or 4 pin sight with .029 fibers. But that's just me. I limit myself to shots under 45 yards when it comes to animals.