I remember back in the eighties, Ford contacted Yamaha to help them design a reliable top end to improve the performance of an existing engine program. At the time, Yamaha was making 180 hp per liter reliably with normal aspiration and Ford hoped for 80 hp a liter and Yamaha, said, is that all? Ford came out with the 3.0L super high output as a result.
Ford SHO V6 engine - Wikipedia, the free encyclopedia
Anyway, different tuning can make a huge difference when variable cam timing in available as well as fuel mapping.
Kioti does publish specs on their engines. Simply because you don't know where to look, doesn't mean Kioti is trying to hide anything.
As you can see the 60hp version not only has more horse power everywhere, it has more torque everywhere. The 60hp version is simply a more efficient engine.
Power (HP) = 1kw = 1.341 HP
Torque (Nm) = 1 newton meter = 0.737562149 foot pounds
The 45 hp version offers a maximum of 109 ft. pounds of torque.
The 60 hp version offers a maximum of 140 ft. pounds of torque.
Basically, the 60 hp version offers roughly 30% more hp and torque. 30% has value. To frame how much more power the 60 hp version of the NX has over the 45 hp version, from 1050 rpm and onward, the NX6010 develops more torque than the peak torque of the NX4510. That extra power has value.
Additionally, at the very end of the following video I broke the box blade (you hear it break). While the company that made the blade redesigned their blade and made it stronger and improved their design, nothing I did in the entire day's worth of work in the video is extreme, harsh or whatever. The video simply illustrates how much force a modern 60 hp CUT can put on the ground.