I have quite a few sets of both. I like them about equally for function except, I don't like the fact that I can't take my expander ball out of the New Dimention dies from Hornady. I like to be able to turn them down a few thousandths if needed to get a proper bullet fit/pull with cast or even jacketed bullets. They usually come about .002" under bullet diameter, but about .004-.005" under works better for a good bullet pull with heavy charges and bullets in large cases. Also, I like to be able to remove the expander and clean inside the die thoroughly. FWIW
I haven't used any Hornady "pistol" dies and so this may not be entirely relevant but I bought two sets of rifle dies made by Hornady because of the price.I ruined several cases with both dies which never happened before.I immediately retired them to the duty of paperweights and ordered RCBS dies for both cartridges.No furthur problems whatsoever.
Received my Hornady 38/357 seater and crimper die today. I really like the bullet seating sleeve assembly- it extends out of the bottom of the die and contacts the bullet to begin aligning it with the case as it enters the base of the die. This made the die a little more forgiving if the bullet wasn't perfectly aligned. In my first trial- seating 148 gr. DEWC- I got minimal variance in OAL and a consistent crimp. I only loaded 50 rounds and set up for one bullet type, but if all my results are this good- I won't be using either my RCBS seater/crimper die or my Lee FCD in the future for 38/357.
I use RCBS dies exclusively but not necessarily because they are "better" than Hornady or others. RCBS has excellent customer service and they can provide some special services that aren't available elsewhere as far as I know.