Jeff
If you compare the MTH funnel flow tank car from 2004 or later with the Atlas funnel flow they compare quite closely. You could even say that Atlas did a nice job of copying the MTH car.
Of course what we really have is an example of two model train companies making 1/48 scale replicas of a common modern tank car. Both are excellent models. And the MTH car has a significant price advantage with an MSRP of $42.95 for the first issue and $54.95 on the most recent Procor and GATX cars from 2011. Take a look at the MTH and Atlas funnel flow tank cars side by side and tell me if you think there is a $15 or greater detail difference.
I doubt it and yes there is a difference!
I have to give credit for MTH in updating their product line. I hope that Atlas O will do the Shorty Beer Car tankers too!