I own a G17, G19 and a G21 all are fine firearms never a jam and all are high cap capable. personaly for 2 legged critters i would take the G21 in 45acp been putting d1cks in the dirt since 1911. The G17 is a hoot to shoot low recoil and 19+1 mags can be had oh any high cap mag from one caliber can fit in any sized Glock of the same caliber such that my 19+1 mags from the G17 also fit in the compact G19 too, just looks funny with an extra 2 inchs of mag hanging out the bottom of the gun :)
I have always suspected that a G17 barrel would fit in a G19 and protrude in front of the slide. If for example one had a need for room to add threads to the end of the barrel. Will they interchange?