Why do you have a different G19 to train with?
Mainly so I am not wearing out my carry gun at the range. The more its is used, the higher the likelyhood of wear parts failing. I actually have three. One I carry, one I practice with, and one as a spare. The spare usually has an advantage arms kit on it. So it sees a fair bit of range time on the frame and fire controls.
To start off I had one that I carried and shot at the range all the time. It was starting to get a pretty high round count. It got to the point where you could tell a noticable difference in the trigger vs a newer gun. So when I started to notice I was wearing it out, I bought a second to use at the range.
I ended up having some trigger issues with the second one and I shipped them both back to Glock for a rebuild. When I did that, I purchased the third to carry while they were away. I don't shoot nearly the volume these days as I did when I wore the first gun out. But I like having the spare.