Questions: locomotive classification, Engine crew preference

I'm still searching out C-16 history and I have two questions that I have not yet found an answer to.
1. When did the D&RGW switch from the weight-based to the tractive effort-based classficiation system (for example, the C-16s were originally classfied as 60Ns)? On the 1923 D&RGW/RGS roster on DRGW.net the narrow gauge locomotives are still classed according to weight.
2. I recall one of our older lurkers, on a past thread discussing C-16s, commenting that at one time he heard that the engine crews preferred the Grant-built C-16s over the Baldwins. I cannot find this suggestion now, and am wondering if this is verifiable.

Thank you,

Josh Bernhard