It's the same market: a compact 9mm. The only difference is the ONE variable of the g19s double-stack magazine, and it's higher capacity.
Whether Glock haters want to admit it or not: EVERY poly manufacturer out there has GOT to analyze Glcok products before taking another step in their R&R process.
The only time the Shield or Nano-like pistols have any advantage is on a person SO SMALL that the print difference can be seen on them, and then you are almost talking about humans the size of children.
Glock doesn't answer to the competitors beneath them, do they? Take a look at the exact size specs of these 3 pistols: the biggest difference is in loaded weight, as the G19 hauls almost double the 9mm.