alright first of all, SHTF threads are discouraged here so from now on we'll refer to this as a survival rifle thread, that is an acceptable topic on this forum. now that all that is out of the way, for my 2 cents.
I am a firm fan of the AR15 and greatly enjoy it as both a sporting/hunting rifle and as a personal/home defense weapon. if all that you are allowed are 4 round magazines then that may tip the balance in favor of more robust semi auto designs able to take long action cartridges but if you really think about it, there is no difference between an AR15 in canada and an AR15 in the United States other than the size of magazines. in your scenario of law and order dissolving, either A) your government can no longer handle the general public and are fighting against you, or you are being invaded by a foreign power and your government(and more than likely ours since we love to poke our noses in other peoples business) is trying to drive them off. since both of our militaries use nearly identical rifles, both would be able to exchange parts, ammo, and magazines with your AR15 so it would be relatively easy in the event of revolution to loot the bad guys for parts, ammo and those coveted 30 round magazines or in the event of invasion you would be able to work in tandem with your home military forces since you use the same caliber and virtually the same rifle with the exception of the trigger group and magazine capacity.
that's just how I see it in the event of a "survival situation". the ability to either use your enemies tools against them or the ability to augment national guard forces are both strong points in favor of the AR15 platform over more traditional styles of semi autos.
ignore my complete lack of capitalization. I still have no problem correcting your grammar.
I never said half the stuff people said I did-Albert Einstein
You can't believe everything you read on the internet-Benjamin Franklin