Without question, if I was behind enemy lines in occupied territory (California), I would not run either a G21 or a G17. I would run a G30S. I do a lot of outdoorsman type activities in the northern Rockies, and the G30S has proven to be an outstanding choice.
I used a Gen 2 and Gen 3 Glock 21 for a work gun, as well as for competition, in addition to carrying one when assigned to a governor's executive protection detail, and can attest to both their durability and accuracy.
Today however, the G30S really makes the most sense, since it is sized like a G19, and comes with 10 round mags.
Hard to beat a G19 sized .45 that comes with 10 round mags for California.