From my engineering perspective: what matters in an engine like a chainsaw is HP. HP is a function of torque x revs. You can have all the torque that you want, but if the chain does not move, you will not cut any wood. Similar to having all the chain speed that you want; without torque it will just bog in the wood. So to get power from a chainsaw and chain, you need both torque and revs. What chainsaw designers try to do is balance chain speed with torque to get a saw that cuts well. If you look at the saw list that we collectively posted, a lot of the HP gains have been in higher revs from the same displacement engines. The flip side to that has been smog requirements and more choked up mufflers to make them quieter. There are other issues like where the peak torque is in the engine, and how steep the torque curve is, etc. That affects how the saw runs, how fast it gets up to speed, etc. I dug up the data on the 191 and did a double take myself. It has the largest displacement and weight, and hence I would have thought it would be the more powerful saw. But that is not the case. My guess is that it is because it is a lower revving saw with a max RPM of 12.5K. To compare, the 200T has a max RPM of 14k. It could also have a choked up muffler, less efficient porting, or a smaller or restricted carb, all which would further reduce the power of a larger displacement engine.