I have to double vote the mavrik. Its a great gun and at 12g your 14 year old will have no problems at all. It has a changable chokes so you can controle the shot to hunt many things and still go trap shooting. A 410 is more for kids in the single diget ages or a guy with a broken arm (has comparable or less kick then an sks with less stopping power)
With the mavrik you can also get tactical stocks, and many add ons (even in canada)
Inserts are legal in canada, you can even legally take a hacksaw to the barrle and stock so long as you keep it with in legal length.
I have owned many auto loader shotguns and unless your willing to shell out $1k the all suck. Seriously, the constantly break and jam, and when somthing does break its usually expensive and beyond the average persons knowledge so you have to pay for a gun smith.
Do on your self a favour, save hundredz, and seriously consider the mavrik, my 8 year old shoots my 12g mav88 and loves it. Its only 12g, I was able to go duck hunting with a pulled shoulder, it hurt a bit but I was able to non the less.