I have owned four Mini 14s and briefly had a Mini 30. I actually bought my first one (a Ranch model) from my college ethics professor. Anyway, I still have one Mini 14, a 580 series, purchased in 2007.
Long story short. Prior to the recent changes (heavier barrel, sometimes a shorter barrel ala the NRA special edition, different sights, etc) Mini 14s had a reputation for poor accuracy. Cold barrel accuracy was often acceptable, the real problems started when you heated one up. Many, though not all, guns would then begin to deliver shotgun like patterns and go from being a 3 or 4 MOA rifle to being an 8 MOA rifle. The GBs and full auto ones which had flash hiders (and the current tactical ones) often suffered less from this problem, causing many to believe that it was barrel harmonics that played a role. Thus there developed a cottage industry of voodoo fixes for Mini 14 accuracy. These involved muzzle attachments, shortening the barrel, changing the gas block, etc (I had an Amega rail that was another claimed fix). Some people had good results with a certain voodoo cure, others would swear the same one was bunk.
Until recently good mags were a problem, but Ruger now sells 20 and 30 (back in production at last) round mags to the general public. Though they are still easily double what a quality AR mag runs.
Parts are harder to come by for Mini 14s. Whereas AR and AK parts are all over the place, it's problematic to even get things like spare firing pins for a Mini 14. Most people are happier getting an AR, though a Mini will be somewhat lighter and handier in stock form than even a relatively basic M4 clone.
Sights are better on the ARs when it comes to irons, and the ARs are easier to scope - more options.