Rgds the MTH cars, the reason that I don't like them is detail & their height. I have a lot of MTH freight cars so I'm not against the brand, but when I look at them closely there are several points that stand out: no poling pockets, the door release mechanism is greatly simplified, the end sill is also simplified, riveting doesn't look right, & no interior detail.
I agree with Dave M, the original Atlas cars look the best. I've been converting my K-Line cars to the original 70's era Atlas trucks when I can find them. I did a couple with Weaver trucks, but the way the 3 rail coupler sits on top of the Weaver truck causes an increase in height - although not as much as the K-Line trucks. If I can find enough 1970's Atlas trucks I'll do the RMT cars too.