A buddy of mine introduced me to the Pietta New Army's a couple of years ago. He had the "Sheriff's Model" with the 5-1/2" barrel. He also had a Kirst conversion cylinder which allowed him to shoot .45 Colt and .45 Schofield ammo.
After I got home from that range session, I was doing a little research on the Pietta and found that Cabella's was having a great sale on them. So, in a short period of time, I ended up with three of the Pietta New Army's. One is the standard 8" and the other two are the 5-1/2" models. I also picked up a Howell's, 5 shot conversion cylinder which fit all three revolvers.
I have shot all three with black powder and with smokeless powder using the conversion cylinder and they have all shot great. I have another friend who has a couple of Uberti New Army's that he uses in cowboy action shooting. They are a little nicer fit and finished than the Pietta's, but they also cost a bit more.
Depending on your budget, you can't go wrong with either one in my opinion....