For the uses I put light rifle to, I prefer the 7.62X39 cartridge over the 5.56 .
That said though, the Mini-30 wasn't designed around the 7.62X39. What I'm saying is that the Mini-30 was an after thought, which as a practical matter, was too little-too late.....meaning that it aint suited very well to cheap (steel-cased) ammo, or to the berdan primers used in even the better (brass-cased) milsurp ammo. Ruger recognized this early on and in fact, recomends that seel cased ammo not be used. I see no warning in their manual against using berdan primed ammo but still, it's becoming rather well known in some circles that regularly using such ammo can/will eventualy lead to a broken firing pin. What those things mean to me is that it's best to use USA brand name ammo, which by extension means ammo made for the commercial market, which is neither cheap nor widely available. By contrast, the Mini-14 can use about any commercial or NATO-marked milsurp that can be found....which BTW, is both widely available and cheaper.
On the other hand, the Mini-30 does have a lot going for it. In my experience, an out of the box Mini-30 is a bit more accurate than an out of the box Mini-14 when both are using comparable ammo. I also beiieve that it's cartridge hits harder, and to me at least, is much easier to reload.
All in all, I guess it depends on what you want the gun for, what you expect it to do, and how mich you expect to actually use it.
Me personaly, when I considered all the pro's 'n con's of both, I picked the Mini-14....but I shoot a lot, which means that I buy ammo by the case...which means that when looking at the cost of (good) .556 ammo VS (good) 7.62X39 ammo, it was perty-plain to me that the cost savings between the two would soon pay for the gun.
But I aint you. Your needs may be quite different than mine....dunno.
DGW