Also finished assembling a trio of Weaver 34-foot PS2 covered hoppers. I love the 34-foot PS2 hopper because it's a scale sized car that works well for smaller layouts. In 3-rail, they'll negotiate O-27 (13.5" radius) curves.
My understanding is that they also carry different commodities, which makes them suitable for various industries. I have a BUNCH of them in various road names which I'm going to eventually switch over to 2-rail.