They are not necessary at all but are the way to go if you don't already have alloy hangers.
You have 7 ranges of adjustment, from 2 wider than the older wide hangers to 1 narrower than the old narrow hangers and inbetween.
You can also adjust toe with them also.
The new hubs have plastic inserts where the bearings go, so less wear on the bearing faces and allows larger or smaller bearings.
Wouldve been nice if they added inserts to change the toe like a couple of other brands but ohwell.
I find getting to the inner hanger is a bit more involving but saying that still a million times better than the Durango.