Years ago (I'm thinking the late 1990's and early 2000's), there was a monthly or per issue feature of 'performance statistics' (weight, stalling amperage, drawbar pull, etc), for various model manufacturer's then current or new models. It was in either Rail Model Journal, Model Railroading, or Railroad Modeler, as I recall. I think there might have been a complete summary table done at some point, of all the models they tested, before the magazine quit publication, about 2005 (they all gave up about the same time). I Model Railroading was eventually bought out by Carstens/Railroad Model Craftsman, and I really haven't seen anything similar run since then.
As others have said, a model 6 axle diesel is not 50% 'more powerful,' than a 4 axle diesel in the model railroading world. Things vary model to model, even from the same manufacturer, as the variables like weight, shaft horsepower, etc, change with each new run of a given model, potentially.
Some people in the past, have done various things such as to make some axles unpowered, on typically 6 axle units, to simulate prototypical motive power capacities.
Hope this helps some.