Earl,
The 70's do make larger cinders, and the exhaust is evident between the two on doubleheaded trains with both classes of engine.
As much as I hate to admit it, I think the Dollywood set up on the front ends was one of the best I've ever seen. They are Master Mechanics on both, but include two or three screens internal to the smokebox. One inside the stack near the top, another in the usual position going from the table plate towards the top of the door, and another from the table plate down part way to the door at an opposing angle. Sort of an internal Ridgway, with a cinder box attached to the bottom of the smokebox. How different this is from other designs may not be much, but the size and quantity of cinders on both engines was hard to detect. I never had a hot one land in my collar or glove the whole time I was employed there, which I couldn't say for the first five miles out of Durango on any trip. The cinders had to be cleaned out every morning, otherwise the bottom screen wasn't as effective and the amount of cinders leaving the stack would increase.
On another note, I don't know how or why it started, but the cartoonish sized coal that is used in Durango is a very easy fix, but not one that I have seen embraced. One thing I look for in the older photographs is the size of coal in the tender, and it appears that the railroad used to purchase smaller sizes. The large coal used currently has a direct impact on the ability of the engine to consume and efficiently use as a fuel. I strongly feel that smaller and appropriate sized coal would make a dent in the amount of cinders created, and the overall tonnage used on a trip including less ash to deal with at the end of a run.