Re: Good steamers?

Well yes, you hit it on the head. It dates back to days of assigned locomotives and it awarded a crew with distinction for maintaining their locomotive. Steaming quality was only part of the equation. Basis for the award was availability and the crews did all their own maintenance, except for heavy repairs. So a mark of a good engine crew was the round number plate awarded for locomotive reliability and availability.
Why would a 'good steamer' not outlast a 'bad steamer'? Well, the awards dated back to the 1910s and a lot of factors can change over the years. Timing had a lot to do with it also. When a class of small and obsolete locomotives came due for retirement the ones that were due for major repairs would be taken out of service first. As each engine in the class came due for regular backshop work they would be scrapped. The Rio Grande got all the miles out of them they could!
So if the 454 and 456, which in the 10s were good engines, were due for major shop work before the 463 and 464 then they would be scrapped first. The last serviceable engines that required major repairs would be the final survivors and if a Gene Autry or a Knott's Berry Farm came along and saved them before the torch could be lit.....voila!
Another reason might be damage inflicted. RGS 40 and 41 were good examples of this. D&RG 402 was a 'round plate' engine on the Rio Grande and 409 was not. They became RGS 40 and 41, respectively, and on that road both had a very high reputation. Of course, by 1916 the assigned engine/crew concept had been stopped. 402/40 was wrecked on Cima Summit in 1943 and was deemed irreparable. Not sure of the nature of the internal damage but I suspect a major break to the boiler and/or steam dome. 409/41 survived to the end of the railroad and is steaming still at Knott's Berry Farm and, rectangular plate or not, is considered a good runner and a fine steamer 120 years after her erection at Baldwin's Philadelphia shops.
Bottom line is what was true in 1910 may not have been true in 1950 or be true in 2001. Many factors can change to take a free steaming reliable engine and change her into a dog and vice-versa.