Wolf Ammo (steel cased) has been working well in my Mini-14. Guns are cheap, it's the ammo that's expensive! Relatively, of course. I figure after a few thousand rounds I've saved enough to by an entirely new rifle. I have used Wolf Ammunition in a Colt AR-15 during a training course and it worked fine the entire 1,200 rounds. Accuracy may not have been as good as some of the others (who were paying 1$ per round versus my 20 cents) but it was hard to notice. Not saying it couldn't damage a gun but I haven't seen it and I've saved a bunch of money.
Probably like most here, I prefer the AR-15 over the Mini but both will work fine.
Now is a good time to buy a Mini-14. It wasn't too long ago that it was difficult to get factory, high capacity magazines. Ruger used to be difficult with that. Now, there seems to be all kind of choices and I agree with Uffda, get only Ruger factory magazines. I've had various problems with the other brands.
Both mine and my friend's newer Mini-14s are 100% reliable. Nice rifles.