We have a mangalitza, and
Yes they are slow growing
They produce a meat which is good for charcuterie.
They are like tamworths in their "see all, test all" view of life
And yes when first encountered they have the "wild boar" tendancy to come at you rather than run away (attack being the best form of defence!) - but if you stand your ground given a little time, they tame down quite easily, and ours is really friendly now and loves a stroke.
In Eastern hungary, where their ancesters originated, they were simply left in the woods for a year or so to fend for themselves, and then harvested, so are very hardy.
Would not recommend them for a first timer, and if you just want great tasting pork, you would do better to have a traditional native breed!