I haven't had any problem with my USA 20 rounders for a Mini 30. But many folks have had fits with them. They must be pretty hit and miss, especially the ones that were produced just before the ban. Mine were made much earlier. Thermold made a good high capacity mag for this gun and as far as I know, these are the only hi-cap Mini-30 mags I haven't heard any complaints about. But they are priced at about $100 each......and that is just too much for me.
Between the two guns, I would rather have an AK. Get yourself one of the fine Arsenal SA M7's ot whatever they are called (I may have the letters backwards) and you should be happy. These are more expensive than a Romanian SAR, but a much better rifle IMHO. And mags are really cheap. You can find plenty of great quality Com Block mags for as little as $7 each.
Don't get me wrong...I like the Mini-30 as well. They are a fine gun, it's just the crappy mags. However, if you are just wanting this as a brush gun for hunting or such, the Mini-30 should be fine. The factory 5 round mags work flawlessly. But if you want something that shoots 30 times, just buy the AK.