We went to 10R in NJ 2 years ago (i think it was), here are some points:
1) There is exactly ZERO (0) cases of any gun owner turning a 15 R mag into ANY police department in NJ.
2) Ranges will not let you use anything over 10R after the cut-off date. They have the ATF and State Troopers to deal with who do inspections...Now if you shoot at an outdoor range with space btwn you and others who is to say what you are using? But I don't want to loose my range privileges at the world class outdoor range I shoot at over 5 rounds, so not something I would do.
3) 45 vs 9mm for SD, yes, 10 R limits certainly change the dynamic of the 9mm H.C. attribute...I never needed any convincing 45 is a better choice for "civilian" SD (I grew up in an era where Alvin York was still a Hero in living peoples memories, see footnote below), but the 10 R limit just sets in in stone...And as always, compare apples:apples. 8+1 45 vs 10+1 9mm in 1911, or 10 45 vs 10 9mm in poly. As long as you can shoot 45 well, it is a done deal...And if not, do the best to optimize your skill with 9mm and you should be fine.
Here is another idea, if you live in a Republican state, get your Governor to declare the entire state a 2A sanctuary (if they haven't already) and announce he will not enforce any mag limits, or any other un-Constitutional 2A LAWS...After all, if Lefty Politician's are the only ones who don't follow federal laws they don't like, and Righties just fall in line when Lefty laws come out, eventually we will loose everything.
At any rate, POTUS will win on 11/3, the attempt at voter fraud will fail, and you guys in Republican states will be able to keep your high-cap mags. Stay strong!
Footnote: This has always summed up the debate for me, and German's are traditionally "big" people
. That is stopping power, all the rest of the debate crumbles against these real-life incidents, especially the major-league Snow-Job coming out of the FBI a few years ago:
"
Alvin York and during World War I he used a M1911 . 45-caliber pistol to stop an attack by six German soldiers while he helped assault a German machine-gun nest near Chatel-Chéhéry on the Western Front. On Oct. 8, 1918, York drew his pistol after emptying his Enfield rifle at the enemy"