This model is defined by many as an adaptation of the Glock 19X (which was developed for the MHS program) to the Law Enforcement and duty needs.
The full grip (of the Glock 17) allows for maximum control while the shortened slide (of the Glock 19) provides various advantages.
Among the pros are faster “clearing of the holster”, shorter sight radius and less reciprocating mass, both due to the shorter slide.
Although a shorter sight radius will render more accurate shots more difficult, it provides a great advantage: the shooter is able to pick up the sights much faster, both on the first shot (from holster or ready position) as well as during follow-up shots.
Along with the sight radius follow-up shots are quicker due to reduced mass moving along the slide. Instead of lightening the slight Glock has simply shortened it, achieving the same result.